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Main
Date: 25 Oct 2006 13:41:06
From: Harold Burton
Subject: What bike computers measure elevation?
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I'm looking for a bike computer with a barometer that will give me the
total climb on a ride. I had an old Cateye that did this but Cateye
doesn't make such a beast any more. Any suggestions?
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Date: 29 Oct 2006 10:18:33
From: Terry Morse
Subject: Re: What bike computers measure elevation?
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Harold Burton wrote:
> I'm looking for a bike computer with a barometer that will give me the
> total climb on a ride. I had an old Cateye that did this but Cateye
> doesn't make such a beast any more. Any suggestions?
I'ee been using a Polar 720i for several years with success. It does
hert rate, speed, cadence (with optional sensor), and altitude. The
altitude is as accurate as a barometric altimeter can provide, and
the cumulative altitude is pretty good. You can also sample your
data in increments as low as 5 seconds, then transfer them to a
desktop computer for analysis.
That may be more than you need. I know some people who are using
this VDO computer:
http://tinyurl.com/yc3t5e
It doesn't have heart rate or data sampling and is much less
expensive.
--
terry morse - Undiscovered Country Tours - http://www.udctours.com/
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Date: 29 Oct 2006 20:12:03
From: Artoi
Subject: Re: What bike computers measure elevation?
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In article <tmorse-DAD03F.10183329102006@news.covad.net >,
Terry Morse <tmorse@spamcop.net > wrote:
> Harold Burton wrote:
>
> > I'm looking for a bike computer with a barometer that will give me the
> > total climb on a ride. I had an old Cateye that did this but Cateye
> > doesn't make such a beast any more. Any suggestions?
>
> I'ee been using a Polar 720i for several years with success. It does
> hert rate, speed, cadence (with optional sensor), and altitude. The
> altitude is as accurate as a barometric altimeter can provide, and
> the cumulative altitude is pretty good. You can also sample your
> data in increments as low as 5 seconds, then transfer them to a
> desktop computer for analysis.
>
> That may be more than you need. I know some people who are using
> this VDO computer:
>
> http://tinyurl.com/yc3t5e
>
> It doesn't have heart rate or data sampling and is much less
> expensive.
I understand that VDO also has models with HRM. Good solid product.
--
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Date: 28 Oct 2006 21:14:54
From: Tom Keats
Subject: Re: What bike computers measure elevation?
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In article <iqh5k21oo3ov9fl9q1np8bosjeba5h2el0@4ax.com >,
carlfogel@comcast.net writes:
>>Digital or analogue wrist-watches?
>
> Or? You rely on only one?
I wouldn't mind having a watch with diurnal & synodic
functions. As long as it doesn't get bashed up while
I'm unloading truck trailers on Friday afternoon.
As it is, I only really need a watch for knowing when
coffee breaks are imminent.
I need an inclinometer for whenever I'm about to fall
over, which is almost never. I need a magnetometer
for ... nothing. Right now my most practical implement
is a Dr Scholl's callus file. When I'm done with my
foot callus, the file might make a good lemon zester.
If I lost my eyesight and my mind, I think I'd rather
just die like a dog in the streets.
But that's just not gonna happen.
I'm gonna die like a dog in the wild.
cheers,
Tom
--
-- Nothing is safe from me.
Above address is just a spam midden.
I'm really at: tkeats [curlicue] vcn [point] bc [point] ca
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Date: 27 Oct 2006 19:50:08
From: Tom Keats
Subject: Re: What bike computers measure elevation?
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In article <vbn4k2dp7uavqj51j82u67376uf5cbbc2r@4ax.com >,
carlfogel@comcast.net writes:
> On Fri, 27 Oct 2006 09:49:06 -0700, tkeats2005@hotmail.com (Tom Keats)
> wrote:
>
> [snip]
>
>>OCD mumber-collecting data-freaks amuse me :-)
>>
>>How many of 'em can go for a computerless ride
>>without suffering withdrawal pangs?
>>
>>
>>cheers,
>> Tom
>
> Dear Tom,
>
> Estimates range from 15.2% to 27.3%,
That sounds rather low to me.
With the right slide rule[*] plus my best reading glasses,
I might be able to calculate those estimates to 3+ significant
decimal positions.
Holy mackerel! I'm one of /you/!
> but there is considerable debate
> about whether the stop-watch function on the wrist-watch should
> eliminate many test subjects.
Digital or analogue wrist-watches?
> Further data is needed.
As it perpetually is, for some rationalism or other.
> Cheers,
Back at'cha,
Tom
> Carl Fogel
[*] It would have to be a Keuffel & Esser with a magnifying cursor.
--
-- Nothing is safe from me.
Above address is just a spam midden.
I'm really at: tkeats [curlicue] vcn [point] bc [point] ca
|
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Date: 27 Oct 2006 21:00:43
From:
Subject: Re: What bike computers measure elevation?
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On Fri, 27 Oct 2006 19:50:08 -0700, tkeats2005@hotmail.com (Tom Keats)
wrote:
>In article <vbn4k2dp7uavqj51j82u67376uf5cbbc2r@4ax.com>,
> carlfogel@comcast.net writes:
>> On Fri, 27 Oct 2006 09:49:06 -0700, tkeats2005@hotmail.com (Tom Keats)
>> wrote:
>>
>> [snip]
>>
>>>OCD mumber-collecting data-freaks amuse me :-)
>>>
>>>How many of 'em can go for a computerless ride
>>>without suffering withdrawal pangs?
>>>
>>>
>>>cheers,
>>> Tom
>>
>> Dear Tom,
>>
>> Estimates range from 15.2% to 27.3%,
>
>That sounds rather low to me.
>
>With the right slide rule[*] plus my best reading glasses,
>I might be able to calculate those estimates to 3+ significant
>decimal positions.
>
>Holy mackerel! I'm one of /you/!
Well, somewhere between 0.987 and 1.007 of us.
>
>> but there is considerable debate
>> about whether the stop-watch function on the wrist-watch should
>> eliminate many test subjects.
>
>Digital or analogue wrist-watches?
Or? You rely on only one?
>
>> Further data is needed.
>
>As it perpetually is, for some rationalism or other.
>
>
>> Cheers,
>
>Back at'cha,
> Tom
>
>> Carl Fogel
>
>[*] It would have to be a Keuffel & Esser with a magnifying cursor.
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Date: 27 Oct 2006 09:49:06
From: Tom Keats
Subject: Re: What bike computers measure elevation?
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In article <45423612@news.nb.nu >,
Lou Holtman <lholremovethis@planet.nl > writes:
> Harold Burton wrote:
>> In article <453fc175$0$34573$742ec2ed@news.sonic.net>,
>> jobst.brandt@stanfordalumni.org wrote:
>>
>>
>>>Bill Baka writes:
>>>
>>>
>>>>>I'm looking for a bike computer with a barometer that will give me
>>>>>the total climb on a ride. I had an old Cateye that did this but
>>>>>Cateye doesn't make such a beast any more. Any suggestions?
>>>
>>>>Anything with a GPS is capable of giving elevation since it will
>>>>resolve not only you latitude and longitude, but also you elevation.
>>>>This comes in handy for GPS enabled cell phones so the 911 operators
>>>>can tell not only where the address is you are calling from but also
>>>>what floor you are on. That might be more than you want to know,
>>>>but the stuff is out there if you want to pay for it.
>>>
>>>GPS does not give reasonable vertical resolution for bicycling.
>>
>>
>>
>>
>>
>> That's for sure. I have a Garmin Etrex Legend that I use for kayaking.
>> I stay within a couple of feet of sea level but the elevation profile it
>> spits out shows variations of 40 feet or more.
>
>
> And you think 40 feet is bad? I always have to smile when people say: 'I
> climbed the Galibier today and my altitude (GPS or barometric) meter
> said 2610 meters instead of the promised 2642 meters'.....
OCD mumber-collecting data-freaks amuse me :-)
How many of 'em can go for a computerless ride
without suffering withdrawal pangs?
cheers,
Tom
--
-- Nothing is safe from me.
Above address is just a spam midden.
I'm really at: tkeats [curlicue] vcn [point] bc [point] ca
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Date: 27 Oct 2006 13:28:12
From:
Subject: Re: What bike computers measure elevation?
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On Fri, 27 Oct 2006 09:49:06 -0700, tkeats2005@hotmail.com (Tom Keats)
wrote:
[snip]
>OCD mumber-collecting data-freaks amuse me :-)
>
>How many of 'em can go for a computerless ride
>without suffering withdrawal pangs?
>
>
>cheers,
> Tom
Dear Tom,
Estimates range from 15.2% to 27.3%, but there is considerable debate
about whether the stop-watch function on the wrist-watch should
eliminate many test subjects.
Further data is needed.
Cheers,
Carl Fogel
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Date: 27 Oct 2006 09:44:53
From:
Subject: Re: What bike computers measure elevation?
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the Garmin Fortrex 101 is nice
all sorts of options, including altitude
check the Amazon listing for more info
under $100 [ebay]
waterboy
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Date: 26 Oct 2006 15:49:26
From: peter
Subject: Re: What bike computers measure elevation?
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Harold Burton wrote:
> In article <453fc175$0$34573$742ec2ed@news.sonic.net>,
> jobst.brandt@stanfordalumni.org wrote:
> > GPS does not give reasonable vertical resolution for bicycling.
> That's for sure. I have a Garmin Etrex Legend that I use for kayaking.
> I stay within a couple of feet of sea level but the elevation profile it
> spits out shows variations of 40 feet or more.
Guess it depends on what you're expecting. You view it as almost
worthless since it sometimes gives variations of 40' while I view it as
great that I finally have a tool that'll almost always give me the
altitude of the mountains I climb to within 40'. It's certainly much
better than the barometric altimeters that I used before (incl. the
Avocet 50) which had much larger errors when there were weather changes
since the last accurate recalibration - or even with constant weather
but conditions that differed from the "standard atmosphere'"
assumptions used to convert pressure readings into altitude values.
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Date: 26 Oct 2006 15:18:46
From: Buck
Subject: Re: What bike computers measure elevation?
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Michael Press wrote:
> Buck, would you direct me to a document or two or three
> on the web that discusses the different things a GPS
> receiver can do? Also a document on the theory and
> methods. Highly technical documents are good for me,
> and I know how to distinguish precision from accuracy.
> I am shopping for a general purpose receiver, but
> prefer to get all the options that make sense for me.
Michael,
Here are some links for you:
http://www.cmtinc.com/gpsbook/index.htm
http://users.erols.com/dlwilson/gps.html
http://edu-observatory.org/gps/gps_accuracy.html
As to what is available on consumer-grade GPS receivers, you might take
a look at this site:
http://www.gps4fun.com/main_compare.php
If you are interested in some advanced mapping and don't like the
software they offer, you can use a program called DNR Garmin to
download the GPS data into a format compatible with a mapping program
like ArcReader or FGIS. Both of these will easily add your GPS data
onto a topo map or aerial photography.
-Buck
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Date: 26 Oct 2006 14:43:48
From: peter
Subject: Re: What bike computers measure elevation?
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bill wrote:
> peter wrote:
> > A good overview of the theory of operation of GPS is at the Trimble
> > website:
> > http://www.trimble.com/gps/index.shtml
>
> This would have been good except for the plug in requirement, which
> never did work with my Firefox.
> > Technical details on the functions, signal formats, etc. are available
> > in this document:
> > http://www.navcen.uscg.gov/pubs/gps/gpsuser/gpsuser.pdf
> >
> Pretty good but looked like an old document.
Yes, but still the best source I've found for the basic system details.
Most newer documents don't go into detail on the formats and signal
characteristics. Of course one does have to realize that some changes
have occurred since '96 - especially turning off the SA dithering and
the implementation of WAAS and other SBAS systems. Further changes
such as additional frequency channels are also being incorporated into
the latest GPS satellites, but not enough yet for them to be used by
our receivers.
> It did confirm my
> suspicions about 3d wanting a fourth satellite in the loop for elevation
> but that only resolves 2 data points into one. There should be no need
> for a civilian GPS unit to need the fourth satellite since I know of no
> biker riding at an altitude of 400 miles or more.
You keep misinterpreting the reason why there's a need for the 4th
satellite signal. Too bad you can't get the Trimble tutorial above
since it goes into a more detailed explanation. It has nothing to do
with distinguishing between only two possible points, but is essential
to get a true 3D fix for any receiver that lacks a precision time
source (i.e. an atomic clock or something directly synched to one).
Receivers that lack atomic clocks need to solve for 4 things: latitude,
longitude, altitude, and time. To solve for 4 variables you need data
from 4 satellites. Now if only 3 satellites can be received, then the
receiver will make do as well as possible by *assuming* that the
altitude hasn't changed since the last fix and will determine the
remaining 3 variables under that assumption.
I've sometimes checked my GPS when I first turn it on upon arrival
after a flight. If it initially just gets a 3 satellite ("2D") fix it
can be off by a few miles since it is still using the last determined
altitude which was likely at 35000' or so while up in the air.
*Assuming* an altitude that's off by miles results in the calculated
position also being off by miles. As soon as the receiver gets
additional satellite signals it corrects the altitude and position -
but until it gets at least 4 satellites it continues to give the wrong
information.
On bike rides the elevation changes are less drastic, but the same
effect occurs under conditions of ginal reception. If only 3
satellites are being received on a climb up a mountain, then the
reported altitude will stay fixed until it suddenly jumps up when the
receiver gets signals from additional satellites. Careful examination
of the tracklog shows that during the time that the reported altitude
was wrong, the position also drifts off from the correct location.
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Date: 26 Oct 2006 22:01:04
From: bill
Subject: Re: What bike computers measure elevation?
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peter wrote:
> bill wrote:
>> peter wrote:
>
>>> A good overview of the theory of operation of GPS is at the Trimble
>>> website:
>>> http://www.trimble.com/gps/index.shtml
>> This would have been good except for the plug in requirement, which
>> never did work with my Firefox.
>
>>> Technical details on the functions, signal formats, etc. are available
>>> in this document:
>>> http://www.navcen.uscg.gov/pubs/gps/gpsuser/gpsuser.pdf
>>>
>> Pretty good but looked like an old document.
>
> Yes, but still the best source I've found for the basic system details.
> Most newer documents don't go into detail on the formats and signal
> characteristics. Of course one does have to realize that some changes
> have occurred since '96 - especially turning off the SA dithering and
> the implementation of WAAS and other SBAS systems. Further changes
> such as additional frequency channels are also being incorporated into
> the latest GPS satellites, but not enough yet for them to be used by
> our receivers.
>
>> It did confirm my
>> suspicions about 3d wanting a fourth satellite in the loop for elevation
>> but that only resolves 2 data points into one. There should be no need
>> for a civilian GPS unit to need the fourth satellite since I know of no
>> biker riding at an altitude of 400 miles or more.
>
> You keep misinterpreting the reason why there's a need for the 4th
> satellite signal. Too bad you can't get the Trimble tutorial above
> since it goes into a more detailed explanation. It has nothing to do
> with distinguishing between only two possible points, but is essential
> to get a true 3D fix for any receiver that lacks a precision time
> source (i.e. an atomic clock or something directly synched to one).
I won't argue that since a Cesium clock and a hand held device aren't
going together any time soon.
> Receivers that lack atomic clocks need to solve for 4 things: latitude,
> longitude, altitude, and time. To solve for 4 variables you need data
> from 4 satellites. Now if only 3 satellites can be received, then the
> receiver will make do as well as possible by *assuming* that the
> altitude hasn't changed since the last fix and will determine the
> remaining 3 variables under that assumption.
That means that back in 2000 the Radio Shack unit actually hit 4
satellites to get an accurate elevation reading. Surprising.
>
> I've sometimes checked my GPS when I first turn it on upon arrival
> after a flight. If it initially just gets a 3 satellite ("2D") fix it
> can be off by a few miles since it is still using the last determined
> altitude which was likely at 35000' or so while up in the air.
Doesn't that hit you as being a kid with a new toy, using it to
determine your altitude? Of course if you are cruising at 35,500 that
something is not good, but do you really want to know?
> *Assuming* an altitude that's off by miles results in the calculated
> position also being off by miles. As soon as the receiver gets
> additional satellite signals it corrects the altitude and position -
> but until it gets at least 4 satellites it continues to give the wrong
> information.
Simple. Quit playing with it on the plane. Kind of like me using the on
board phone on a commuter flight to LA with my phone card and forgetting
that it was about $3 a minute. I got the bill and quit that in a hurry.
No more chatting with the wife at 30,000 feet.
>
> On bike rides the elevation changes are less drastic, but the same
> effect occurs under conditions of ginal reception. If only 3
> satellites are being received on a climb up a mountain, then the
> reported altitude will stay fixed until it suddenly jumps up when the
> receiver gets signals from additional satellites. Careful examination
> of the tracklog shows that during the time that the reported altitude
> was wrong, the position also drifts off from the correct location.
The unfortunate conclusion is that we need about twice as many
satellites to ensure coverage in adverse conditions, which may not be
practical unless 6 satellites at once can be launched and then the
orbits juggled by on board booster rockets once they are up there.
Launching another constellation with single satellite rocket launches
would cost more than I feel like paying tax money for.
>
--
Bill (Sleepless biker) Baka
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Date: 26 Oct 2006 12:36:41
From: peter
Subject: Re: What bike computers measure elevation?
|
Michael Press wrote:
> would you direct me to a document or two or three
> on the web that discusses the different things a GPS
> receiver can do? Also a document on the theory and
> methods. Highly technical documents are good for me,
> and I know how to distinguish precision from accuracy.
> I am shopping for a general purpose receiver, but
> prefer to get all the options that make sense for me.
Here are some to get you started.
A good overview of the theory of operation of GPS is at the Trimble
website:
http://www.trimble.com/gps/index.shtml
A website with quite a few reviews of different GPS receivers and also
with extensive lists of additional GPS resources is:
http://gpsinformation.net
Technical details on the functions, signal formats, etc. are available
in this document:
http://www.navcen.uscg.gov/pubs/gps/gpsuser/gpsuser.pdf
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Date: 26 Oct 2006 21:10:45
From: bill
Subject: Re: What bike computers measure elevation?
|
peter wrote:
> Michael Press wrote:
>> would you direct me to a document or two or three
>> on the web that discusses the different things a GPS
>> receiver can do? Also a document on the theory and
>> methods. Highly technical documents are good for me,
>> and I know how to distinguish precision from accuracy.
>> I am shopping for a general purpose receiver, but
>> prefer to get all the options that make sense for me.
>
> Here are some to get you started.
>
> A good overview of the theory of operation of GPS is at the Trimble
> website:
> http://www.trimble.com/gps/index.shtml
This would have been good except for the plug in requirement, which
never did work with my Firefox.
>
> A website with quite a few reviews of different GPS receivers and also
> with extensive lists of additional GPS resources is:
> http://gpsinformation.net
Good site for buyers.
>
> Technical details on the functions, signal formats, etc. are available
> in this document:
> http://www.navcen.uscg.gov/pubs/gps/gpsuser/gpsuser.pdf
>
Pretty good but looked like an old document. It did confirm my
suspicions about 3d wanting a fourth satellite in the loop for elevation
but that only resolves 2 data points into one. There should be no need
for a civilian GPS unit to need the fourth satellite since I know of no
biker riding at an altitude of 400 miles or more. It should be blatantly
obvious that a civilian, and most military personnel except for
astronauts will be on the data point within ten miles of sea level.
On the flip side of that comment, astronauts don't have a latitude or
longitude problem. As to the civilian accuracy of 100 meters, that is
wrong for today, or we would not have the 'ugh' Tom Tom units that can
tell what street you are on.
--
Bill (Sleepless biker) Baka
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Date: 26 Oct 2006 11:54:42
From: Dirtroadie
Subject: Re: What bike computers measure elevation?
|
jobst.brandt@stanfordalumni.org wrote:
> I guess you don't understand what "within their resolution" means,
> which doesn't get any better if that resolution is poor. It just
> collects greater errors.
Are we speaking of "resolution" or "accuracy?" A typical GPS unit has a
resolution of 1ft/1 meter. As to accuracy, I think if you had actually
used a GPS receiver you might have a substantially different
understanding. You have not used one, have you?
> It's still not useful for bicycling altimeters.
Perhaps you should preface your statement with "I was under the
erroneous impression that..."
I'm not sure what your definition of "useful" is, but please don't be
making broad erroneous generalizations about the usefulness or accuracy
of something you appear to have no hands-on familiarity with.
See this example of a GPS "track" recently recorded on a simple
handlebar mounted consumer GPS receiver with the profile displayed
using Topofusion software.
http://members.aol.com/dirtroadie/bike/Cliffs_Profile.jpg
While there is some variation to be seen, there are no dramatic errors.
And here's the top portion of the the same track projected (via the
same software) onto the corresponding USGS topo.
http://members.aol.com/dirtroadie/bike/CliffsTopDetail.jpg
Note the elevation on the topo as compared to the GPs profile. I'm not
sure what you consider to be sufficient resolution or accuracy but the
GPS measurement and the map indication are virtually identical. (I am
actually less impressed by the GPS accuracy than by the accuracy of
ancient USGS topographic maps, which generally predate any form of
electronic technology.)
And the software (using only GPS data) accurately calculates the "total
climbing" to be essentially the same as that which is found by merely
subtracting the base elevation from that of the top, which accurately
reflects the steady nature of this particular climb.
> Which instrument do you suggest as a bicycle altimeter and speedometer/
> odometer?
I have priily used various Garmin units. My favorite for cycling
use is the Foretrex 201, priily for its convenient and compact size
and shape. It ofers all the basic functions of a typical cyclometer
and works well with the aforementioned TopoFusion software.
DR
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| | |
Date: 28 Oct 2006 10:24:48
From: Lou Holtman
Subject: Re: What bike computers measure elevation?
|
Dirtroadie wrote:
> jobst.brandt@stanfordalumni.org wrote:
>
>
>>I guess you don't understand what "within their resolution" means,
>>which doesn't get any better if that resolution is poor. It just
>>collects greater errors.
>
>
> Are we speaking of "resolution" or "accuracy?" A typical GPS unit has a
> resolution of 1ft/1 meter. As to accuracy, I think if you had actually
> used a GPS receiver you might have a substantially different
> understanding. You have not used one, have you?
>
>
>>It's still not useful for bicycling altimeters.
>
>
> Perhaps you should preface your statement with "I was under the
> erroneous impression that..."
> I'm not sure what your definition of "useful" is, but please don't be
> making broad erroneous generalizations about the usefulness or accuracy
> of something you appear to have no hands-on familiarity with.
>
> See this example of a GPS "track" recently recorded on a simple
> handlebar mounted consumer GPS receiver with the profile displayed
> using Topofusion software.
> http://members.aol.com/dirtroadie/bike/Cliffs_Profile.jpg
> While there is some variation to be seen, there are no dramatic errors.
>
>
> And here's the top portion of the the same track projected (via the
> same software) onto the corresponding USGS topo.
> http://members.aol.com/dirtroadie/bike/CliffsTopDetail.jpg
>
> Note the elevation on the topo as compared to the GPs profile. I'm not
> sure what you consider to be sufficient resolution or accuracy but the
> GPS measurement and the map indication are virtually identical. (I am
> actually less impressed by the GPS accuracy than by the accuracy of
> ancient USGS topographic maps, which generally predate any form of
> electronic technology.)
> And the software (using only GPS data) accurately calculates the "total
> climbing" to be essentially the same as that which is found by merely
> subtracting the base elevation from that of the top, which accurately
> reflects the steady nature of this particular climb.
>
>
>>Which instrument do you suggest as a bicycle altimeter and speedometer/
>>odometer?
>
>
> I have priily used various Garmin units. My favorite for cycling
> use is the Foretrex 201, priily for its convenient and compact size
> and shape. It ofers all the basic functions of a typical cyclometer
> and works well with the aforementioned TopoFusion software.
Another example. This summer I went from Corvara to Arabba over the
Passo Campolongo (altitude 1872 meters). In the descent to Arabba hell
broke loose weatherwise so I decided to go back. The altitude graph
should be symmetric around the 10.something km k. It was recorded by
a Garmin Edge 305. Enjoy ;-)
http://home.planet.nl/~holtm072/plaatjes/AltitudeExample.jpg
We just have to live with the limitations.
Lou
--
Posted by news://news.nb.nu
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Date: 26 Oct 2006 09:24:44
From: peter
Subject: Re: What bike computers measure elevation?
|
Booker C. Bense wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
>
> In article <W1O%g.15990$GR.9136@newssvr29.news.prodigy.net>,
> bill <"just use comcast", "you know the drill for no spam bots."> wrote:
> >>
> >The information is there for the taking since a GPS uses the
> >triangulation of information from 3 satellites meaning you can be at one
> >and only one point in space (hopefully on the Earth).
>
> The GPS's that display altitude generally
> use a internal barometer to do it. It is only very recently
> with the addition of WAAS signal that GPS can have any
> reasonable accuracy wrt altitude.
No, all the handheld GPS receivers I've ever used or seen have had the
ability to display altitudes, but very few of them have had barometric
sensors. And while WAAS has improved accuracy, it is by no means
necessary to get good enough altitude data to be useful for bicycling
or similar applications.
> Even then most GPS's can
> not approach the accuracy of a recently calibrated barometer.
Actually, most barometers only report atmospheric pressure and not
altitude at all, but I presume you mean pressure-based altimeters.
Then it depends on the specifications of the particular instrument and
how recently it was calibrated compared to weather-related changes in
the pressure.
The GPS model I've been using as my bicycle cyclometer for the last 7
years is a Garmin eMap, which is a receiver that does *not* support
WAAS. Studies I've done with it over the years have shown that the
altitude indications are within 35' over 95% of the time when the unit
has reasonable reception (at least 5 satellites in view). This is
consistent with what was found by David Wilson as reported at:
http://users.erols.com/dlwilson/gpsvert.htm
He gives an RMS accuracy of the eMap of 6 meters which corresponds to a
95% accuracy of just under 12 meters, or 39'. WAAS-equipped receivers
could improve on that accuracy by up to a factor of two when the
geosynch. satellites can be seen (much more frequently the case now
since the new ones have come on line).
Here's an example of the data the eMap gives on actual bike rides:
http://home.comcast.net/~prathman/Image33.gif
This shows two rides of the same course on two different days. One
ride is shown in red and the other in blue with the horizontal plots of
position superimposed on each other and the elevation plots below.
Small differences can be seen in the two plots due to measurement
variations, but they are in good agreement in general and are also in
good agreement with 1:24000 USGS topo maps with which I've compared
them.
> If you want altitude data, the Garmin Edge 205/305 is a very nice if
> pricy cyclometer.
But unfortunately does not provide any mapping capability to show you
where you are and what roads will take you to your destination or
useful information on a tour like where nearby restaurants or grocery
stores are located.
So I find other handheld GPS models to be far more useful - and they
also provide altitude data plus typical cyclometer functions (odometer,
total average and moving average speeds, etc.)
|
| | |
Date: 26 Oct 2006 13:14:06
From: Tim McNamara
Subject: Re: What bike computers measure elevation?
|
In article <1161879884.472011.268210@m7g2000cwm.googlegroups.com >,
"peter" <prathman@comcast.net > wrote:
> Booker C. Bense wrote:
> > -----BEGIN PGP SIGNED MESSAGE-----
> >
> > In article <W1O%g.15990$GR.9136@newssvr29.news.prodigy.net>, bill
> > <"just use comcast", "you know the drill for no spam bots."> wrote:
> > >>
> > >The information is there for the taking since a GPS uses the
> > >triangulation of information from 3 satellites meaning you can be
> > >at one and only one point in space (hopefully on the Earth).
> >
> > The GPS's that display altitude generally use a internal barometer
> > to do it. It is only very recently with the addition of WAAS signal
> > that GPS can have any reasonable accuracy wrt altitude.
>
> No, all the handheld GPS receivers I've ever used or seen have had
> the ability to display altitudes, but very few of them have had
> barometric sensors. And while WAAS has improved accuracy, it is by no
> means necessary to get good enough altitude data to be useful for
> bicycling or similar applications.
Precisely. In our brevet series in 2005, two riders used GPS units for
guidance as well as to record information about the rides. One unit
measured 10,500 feet of climbing and the other 9,817 over the 191 miles
on the day. That's quite a gin of error- a difference of 683 feet or
7%. By comparison, the mapping software predicted total climbing of
11,144 feet. The mapping software estimated at least 10% more climbing
than any of the GPS units measured on each of the four brevets.
Personally I have a much more calibrated gauge of climbing: flat,
rolling, hilly, and wowser. I don't really need to know the numbers.
It's just a bike ride. I'm generally more concerned with the fun than
the stats.
|
| | | |
Date: 26 Oct 2006 19:04:48
From: bill
Subject: Re: What bike computers measure elevation?
|
Tim McNaa wrote:
> In article <1161879884.472011.268210@m7g2000cwm.googlegroups.com>,
> "peter" <prathman@comcast.net> wrote:
>
>> Booker C. Bense wrote:
>>> -----BEGIN PGP SIGNED MESSAGE-----
>>>
>>> In article <W1O%g.15990$GR.9136@newssvr29.news.prodigy.net>, bill
>>> <"just use comcast", "you know the drill for no spam bots."> wrote:
>>>> The information is there for the taking since a GPS uses the
>>>> triangulation of information from 3 satellites meaning you can be
>>>> at one and only one point in space (hopefully on the Earth).
>>> The GPS's that display altitude generally use a internal barometer
>>> to do it. It is only very recently with the addition of WAAS signal
>>> that GPS can have any reasonable accuracy wrt altitude.
>> No, all the handheld GPS receivers I've ever used or seen have had
>> the ability to display altitudes, but very few of them have had
>> barometric sensors. And while WAAS has improved accuracy, it is by no
>> means necessary to get good enough altitude data to be useful for
>> bicycling or similar applications.
This is why some of the posters ragging on my 'lack of knowledge' have
gotten me testy. I had a friend in 2000 who had a cheap Radio Shack GPS
that showed altitude and it was within 5 feet of the posted altitude on
the welcome sign for the town we were in. I really doubt that WAAS was
on that Radio Shack unit back then.
My comment on barometric based units was actually at least semi-serious.
If your barometer pressure drops and it shows you going rapidly uphill
as a result you can be fairly sure a sudden storm is going to nail you.
Sailors live 'literally' by paying attention to this and a barometer
based altimeter could conceivably save your life if a thunderstorm was
coming fast. I have seen the effects of a big lightning strike and you
'DON'T' want to get hit.
>
> Precisely. In our brevet series in 2005, two riders used GPS units for
> guidance as well as to record information about the rides. One unit
> measured 10,500 feet of climbing and the other 9,817 over the 191 miles
> on the day. That's quite a gin of error- a difference of 683 feet or
> 7%. By comparison, the mapping software predicted total climbing of
> 11,144 feet. The mapping software estimated at least 10% more climbing
> than any of the GPS units measured on each of the four brevets.
>
> Personally I have a much more calibrated gauge of climbing: flat,
> rolling, hilly, and wowser. I don't really need to know the numbers.
> It's just a bike ride. I'm generally more concerned with the fun than
> the stats.
Just have fun riding, or get serious and rig a Blackberry or something
for a data recorder. The possibilities are endless but depend on how
deep your pockets are lined with money.
--
Bill (Sleepless biker) Baka
|
| |
Date: 26 Oct 2006 06:58:14
From: AustinMN
Subject: Re: What bike computers measure elevation?
|
bill wrote:
> Solvang Cyclist wrote:
> > bill <bbaka@c-o-m-c-a-s-t.net> wrote in news:IfO%g.15997$GR.1026
> > @newssvr29.news.prodigy.net:
> >
> >> Ask a 911 operator who gets an emergency call from someone in a high
> >> rise and does not know what floor they are on. The newer GPS enabled
> >> phones are supposed to give them that information.
> >
> > I don't believe this is true. Even the newer GPS receivers have VERY POOR
> > vertical accuracy. Even if the vertical accuracy was as good as the
> > horizontal, that's only about 30 feet. Great for finding you on the
> > ground, but +/- 30 feet would be a range of 7 floors of a typical
> > building. As I recall, the current requirements for Mobile E911 (Enhanced
> > 911) service - which has been delayed several times - is on the order of
> > several hundred feet in the horizontal and no requirements for altitude
> > information.
> >
> > Also, it actually takes 4 not 3 satellites to get a location. That's
> > because the system is "triangulating" in three dimensions - not just two.
> >
> > Cheers,
> > David
> >
> The intersection of 2 spheres is a big circle. 3 spheres gives you 2
> points, one on the surface of the earth, and one either inside the earth
> or out in space. 4 would eliminate that last ambiguity but realistically
> how would you go from on a bike to 400 or so miles out in space in the
> blink of an eye.
So far, so good - except for one bad assumtion.
> The vertical accuracy is just as good as the latitude
> and longitude, so if there is any limitation, it is either the
> instrument vendor not taking it seriously or the government putting a
> limit on it.
Totally wrong. The accuracy in any direction is dependent on the
angular separation of the sattelites from the receiver's point of view.
Since most of the time, the received sattelites are nearly coplanar,
the vertical information is essentially useless because the gin of
error is so exaggerated. Aircraft GPS receivers have to track the
positions of the sattellites they are receiving in order to avoid
accuracy problems for this reason. It is possible to receive as many
as 5 sattelites at a time and have them line up nearly perfectly -
making *all* of the GPS information useless, not just the altitude.
BTW, the sattelite constellation that was in place several years ago
guaranteed this would happen at least once a day somewhere on earth.
> There used to be a military mandated block on x-y accuracy
> for consumers until about 5 years ago when 911 operators started wanting
> it to locate accident (and lost) victims. The electronics is capable of
> about 3 feet (nanoseconds) so a 7 floor range strikes me as ridiculous.
Bill, Bill, Bill. The removal of the military fudging of the civilian
GPS channels had nothing to do with 911 operators, it had to do with
civilian aviation - and nothing else. What 911 operators wanted was
better locations from cell phones - GPS or not - which means better
information than simply which cell the call came from. The direction
most of the industry is going in is to get that information from the
cell towers, not from a GPS signal. Bother to get your facts right
before vomiting up your garbage.
Austin
|
| | |
Date: 26 Oct 2006 15:18:34
From: bill
Subject: Re: What bike computers measure elevation?
|
AustinMN wrote:
> bill wrote:
>> Solvang Cyclist wrote:
>>> bill <bbaka@c-o-m-c-a-s-t.net> wrote in news:IfO%g.15997$GR.1026
>>> @newssvr29.news.prodigy.net:
>>>
>>>> Ask a 911 operator who gets an emergency call from someone in a high
>>>> rise and does not know what floor they are on. The newer GPS enabled
>>>> phones are supposed to give them that information.
>>> I don't believe this is true. Even the newer GPS receivers have VERY POOR
>>> vertical accuracy. Even if the vertical accuracy was as good as the
>>> horizontal, that's only about 30 feet. Great for finding you on the
>>> ground, but +/- 30 feet would be a range of 7 floors of a typical
>>> building. As I recall, the current requirements for Mobile E911 (Enhanced
>>> 911) service - which has been delayed several times - is on the order of
>>> several hundred feet in the horizontal and no requirements for altitude
>>> information.
>>>
>>> Also, it actually takes 4 not 3 satellites to get a location. That's
>>> because the system is "triangulating" in three dimensions - not just two.
>>>
>>> Cheers,
>>> David
>>>
>> The intersection of 2 spheres is a big circle. 3 spheres gives you 2
>> points, one on the surface of the earth, and one either inside the earth
>> or out in space. 4 would eliminate that last ambiguity but realistically
>> how would you go from on a bike to 400 or so miles out in space in the
>> blink of an eye.
>
> So far, so good - except for one bad assumtion.
>
>> The vertical accuracy is just as good as the latitude
>> and longitude, so if there is any limitation, it is either the
>> instrument vendor not taking it seriously or the government putting a
>> limit on it.
>
> Totally wrong. The accuracy in any direction is dependent on the
> angular separation of the sattelites from the receiver's point of view.
> Since most of the time, the received sattelites are nearly coplanar,
> the vertical information is essentially useless because the gin of
> error is so exaggerated. Aircraft GPS receivers have to track the
> positions of the sattellites they are receiving in order to avoid
> accuracy problems for this reason. It is possible to receive as many
> as 5 sattelites at a time and have them line up nearly perfectly -
> making *all* of the GPS information useless, not just the altitude.
> BTW, the sattelite constellation that was in place several years ago
> guaranteed this would happen at least once a day somewhere on earth.
Once a day somewhere on earth I can live with. Thinking a bit more about
it I have to give you the vertical accuracy bit since the intersection
of the 3 spheres is more of a vertical line with some fudge room a lot
more than the latitude and longitude. My bad.
>
>> There used to be a military mandated block on x-y accuracy
>> for consumers until about 5 years ago when 911 operators started wanting
>> it to locate accident (and lost) victims. The electronics is capable of
>> about 3 feet (nanoseconds) so a 7 floor range strikes me as ridiculous.
>
> Bill, Bill, Bill. The removal of the military fudging of the civilian
> GPS channels had nothing to do with 911 operators, it had to do with
> civilian aviation - and nothing else.
Hikers too. Bob Pease of National Semiconductor did an article on it
when the civilian sector was being fudged. He took several readings and
found that they came out to be about 100 feet or so from his actual
position and after finding out all the false readings he could deduce
where he was at. That would have been a total pain for the average
person back then.
What 911 operators wanted was
> better locations from cell phones - GPS or not - which means better
> information than simply which cell the call came from. The direction
> most of the industry is going in is to get that information from the
> cell towers, not from a GPS signal.
Unless it has been changed the best location technique was to determine
which tower the signal came from and if any other tower had any amount
of signal. Transit time to the tower could locate the phone on a
circumference around the tower but as far as I know there is no way to
get a directional signal from a tower other than comparing signal
strengths from antennas on different sides of the tower. This has no
bearing on the original question where the rider wanted elevation.
It is handy for a 911 operator to send the response cars in the right
general direction, on that I agree, but a tower is just not a GPS device.
Bother to get your facts right
> before vomiting up your garbage.
Bother to have some civility, asshole. If I wanted to give technical
lessons I would have had to waste time finding web pointers. This was a
general answer and not intended as a class.
>
> Austin
>
--
Bill (Sleepless biker) Baka
|
| |
Date: 26 Oct 2006 06:49:23
From: Buck
Subject: Re: What bike computers measure elevation?
|
Dan wrote:
> With USGS topographical maps
> available on line these days, it is easy to check elevations too.
It depends on how accurate you want. The maps are classified according
to the scale at which the data was captured and the extent which the
map covers.
The vertical standard for USGS 1:24,000 topographic maps is 90% of all
points tested must be within 1/2 of one contour line interval.
The horizontal standard for USGS 1:24,000 topographic maps is 90% of
all points tested must be within 40 feet of their true location.
In many areas, 1:24,000 maps are available. The contour intervals vary
by location. In some places, they are as frequent as every ten feet, in
others it can be much more coarse.
The next scale available is 1:100,000 and after that, 1:250,000. These
are, of course, much less accurate than the 1:24,000 maps.
-Buck
|
| | |
Date: 26 Oct 2006 20:17:56
From: Dan
Subject: Re: What bike computers measure elevation?
|
Buck wrote:
> Dan wrote:
>> With USGS topographical maps
>> available on line these days, it is easy to check elevations too.
>
> It depends on how accurate you want. The maps are classified according
> to the scale at which the data was captured and the extent which the
> map covers.
>
> The vertical standard for USGS 1:24,000 topographic maps is 90% of all
> points tested must be within 1/2 of one contour line interval.
>
> The horizontal standard for USGS 1:24,000 topographic maps is 90% of
> all points tested must be within 40 feet of their true location.
>
> In many areas, 1:24,000 maps are available. The contour intervals vary
> by location. In some places, they are as frequent as every ten feet, in
> others it can be much more coarse.
>
> The next scale available is 1:100,000 and after that, 1:250,000. These
> are, of course, much less accurate than the 1:24,000 maps.
>
> -Buck
>
Geez, you sound like a USGS guy. My Dad was a field man for the survey.
I spent many summer days helping him lug a theodolite up peaks and
recording angles in little books while he peered through the scope.
Anyway, The accuracy provided by topos is good enough to verify my bike
altimeter readings.
|
| |
Date: 26 Oct 2006 06:34:18
From: Buck
Subject: Re: What bike computers measure elevation?
|
bill wrote:
> I said the data is there and you can use it if you want to buy a decent
> GPS enabled (insert whatever) device. That is neither silly nor
> meaningless. A barometer can be very misleading if the weather changes
> although it might tell you to go home if your altitude reading goes up
> on a descent (storm coming at you fast).
Bill, you are showing your ignorance. Here are a few points:
1. GPS does not function inside of buildings. GPS requires a clear view
of the sky to receive the satellite signals.
2. GPS is roughly three times less accurate vertically than it is
horizontally. While some consumer-grade GPS units can achieve 3 meter
horizontal accuracy, that is only when they have an unobstructed view
of the southern sky and can receive error correction from WAAS. WAAS is
a system designed for aircraft, which usually have a clear view of the
southern sky where the satellite is parked in geosynchronous orbit.
Otherwise, they are accurate within 15 to 30 meters, depending on
conditions. If the GPS isn't designed to inform the user of the current
conditions (PDOP), then the user has no way of knowing the horizontal
precision (which is used as a proxy for accuracy). Remember, vertical
measurement is three times LESS accurate than horizontal.
3. GPS uses a process called trilateration, not triangulation.
Triangulation uses the angles between objects to estimate a position.
Trilateration uses distances from different objects to estimate
positions. GPS functions by measuring the time it takes for the signal
from each satellite in its "view" to reach the receiver. This, combined
with the known position of the satellite (the ephemeris is encoded in
the signal), allows the GPS receiver to calculate its position.
4. GPS is notoriously inaccurate in cities because of multi-path
errors. GPS signals get bounced around between buildings and result in
inaccurate measures of distance.
5. GPS is inaccurate in areas of high topographic relief partly because
of multipath errors, but partly because of the hills blocking a view of
the sky (buildings also cause this problem).
6. Many consumer-grade GPS units do not report much of the information
available in or calculable from the priy satellite signal. Measures
of error such as HDOP or PDOP are often left out. Even something as
simple as whether or not the device is receiving a differential
correction signal is often left out. It is not surprising that many
cell phones don't report an estimated elevation.
7. Anything that blocks the receiver's view of the sky can introduce
errors. As part of my work, I have the opportunity to train people on
mapping and survey-grade GPS. To help students become aware of the
limitations, I send them into the forest to retrieve flagging material
I left at specific coordinates. They are always amazed at how difficult
it can be to get a good signal when they are surrounded by trees.
8. Cell phones are designed to use trilateration based on cell towers
if the GPS cannot receive a signal. This is a straight-line distance
and does not contain a provision for measuring elevation. The method
just isn't as sophisticated as GPS.
I hope you have read and thought about these common misconceptions
concerning GPS. I hope you will consider them before speaking as if you
are an authority on the technology.
-Buck
|
| | |
Date: 26 Oct 2006 19:23:31
From: Michael Press
Subject: Re: What bike computers measure elevation?
|
In article
<1161869658.419452.233150@m7g2000cwm.googlegroups.com >,
"Buck" <bicyclebuck@gmail.com > wrote:
[...]
> 6. Many consumer-grade GPS units do not report much of the information
> available in or calculable from the priy satellite signal. Measures
> of error such as HDOP or PDOP are often left out. Even something as
> simple as whether or not the device is receiving a differential
> correction signal is often left out. It is not surprising that many
> cell phones don't report an estimated elevation.
Buck, would you direct me to a document or two or three
on the web that discusses the different things a GPS
receiver can do? Also a document on the theory and
methods. Highly technical documents are good for me,
and I know how to distinguish precision from accuracy.
I am shopping for a general purpose receiver, but
prefer to get all the options that make sense for me.
Thank you.
--
Michael Press
|
| | |
Date: 26 Oct 2006 15:03:00
From: bill
Subject: Re: What bike computers measure elevation?
|
Buck wrote:
> bill wrote:
>> I said the data is there and you can use it if you want to buy a decent
>> GPS enabled (insert whatever) device. That is neither silly nor
>> meaningless. A barometer can be very misleading if the weather changes
>> although it might tell you to go home if your altitude reading goes up
>> on a descent (storm coming at you fast).
>
>
> Bill, you are showing your ignorance. Here are a few points:
>
> 1. GPS does not function inside of buildings. GPS requires a clear view
> of the sky to receive the satellite signals.
I haven't tried it inside buildings, but I would expect the signal to be
severely attenuated in a building with any metal content.
>
> 2. GPS is roughly three times less accurate vertically than it is
> horizontally. While some consumer-grade GPS units can achieve 3 meter
> horizontal accuracy, that is only when they have an unobstructed view
> of the southern sky and can receive error correction from WAAS. WAAS is
> a system designed for aircraft, which usually have a clear view of the
> southern sky where the satellite is parked in geosynchronous orbit.
> Otherwise, they are accurate within 15 to 30 meters, depending on
> conditions. If the GPS isn't designed to inform the user of the current
> conditions (PDOP), then the user has no way of knowing the horizontal
> precision (which is used as a proxy for accuracy). Remember, vertical
> measurement is three times LESS accurate than horizontal.
This does not provoke me to go and grab a technical article to post here
since it would be lost on most of the group. X, Y, and Z can be
determined from the intersection of 3 spheres as determined by transit
time to the 3 satellites generating the reference signal. In the past
the military was responsible for limiting accuracy of the X and Y
components, and I am not too sure whether they still have a limit on
civilian use of the vertical component.
>
> 3. GPS uses a process called trilateration, not triangulation.
> Triangulation uses the angles between objects to estimate a position.
> Trilateration uses distances from different objects to estimate
> positions. GPS functions by measuring the time it takes for the signal
> from each satellite in its "view" to reach the receiver. This, combined
> with the known position of the satellite (the ephemeris is encoded in
> the signal), allows the GPS receiver to calculate its position.
I knew that, but triangulation is an easier term to grasp.
>
> 4. GPS is notoriously inaccurate in cities because of multi-path
> errors. GPS signals get bounced around between buildings and result in
> inaccurate measures of distance.
We didn't start this over cities, but rather how to measure elevation on
a bicycle in the mountains. On the bicycle groups that would probably be
the only use since if you can get so lost in a city that you need GPS
you probably should not be out on your own.
>
> 5. GPS is inaccurate in areas of high topographic relief partly because
> of multipath errors, but partly because of the hills blocking a view of
> the sky (buildings also cause this problem).
Good reason not to try it in a valley. Can we just get over this and say
that due to the microwave frequencies involved it is basically a line of
sight instrument? State the obvious once and be done with it.
>
> 6. Many consumer-grade GPS units do not report much of the information
> available in or calculable from the priy satellite signal. Measures
> of error such as HDOP or PDOP are often left out. Even something as
> simple as whether or not the device is receiving a differential
> correction signal is often left out. It is not surprising that many
> cell phones don't report an estimated elevation.
I did mention that it depends on how much cash you want to waste. Maybe
if people carried a GPS enabled phone/camera/MP3/computer that option
would be a no brainer. Personally, I have better things to waste money on.
>
> 7. Anything that blocks the receiver's view of the sky can introduce
> errors. As part of my work, I have the opportunity to train people on
> mapping and survey-grade GPS. To help students become aware of the
> limitations, I send them into the forest to retrieve flagging material
> I left at specific coordinates. They are always amazed at how difficult
> it can be to get a good signal when they are surrounded by trees.
Do they understand microwave concepts?
>
> 8. Cell phones are designed to use trilateration based on cell towers
> if the GPS cannot receive a signal. This is a straight-line distance
> and does not contain a provision for measuring elevation. The method
> just isn't as sophisticated as GPS.
That just gives a very rough estimate for emergency services or for the
police to chase a criminal.
>
> I hope you have read and thought about these common misconceptions
> concerning GPS. I hope you will consider them before speaking as if you
> are an authority on the technology.
I know how it works and I was not trying to give a damned class.
You can, I don't care. There is no test at the end of my posts.
>
> -Buck
>
--
Bill (Sleepless biker) Baka
|
| | |
Date: 26 Oct 2006 11:18:16
From: Roger Zoul
Subject: Re: What bike computers measure elevation?
|
Buck wrote:
::
:: Bill, you are showing your ignorance. Here are a few points:
::
Thanks for the info, Buck!
|
| | | |
Date: 27 Oct 2006 12:46:26
From: R Brickston
Subject: Re: What bike computers measure elevation?
|
On Thu, 26 Oct 2006 11:18:16 -0400, "Roger Zoul"
<rogerzoul2@hotmail.com > wrote:
>Buck wrote:
>::
>:: Bill, you are showing your ignorance. Here are a few points:
>::
>
>Thanks for the info, Buck!
>
Only on Planet Baka. The funny part is Billy's follow up "excuse
post."
|
| | | | |
Date: 27 Oct 2006 22:10:11
From: bill
Subject: Re: What bike computers measure elevation?
|
R Brickston wrote:
> On Thu, 26 Oct 2006 11:18:16 -0400, "Roger Zoul"
> <rogerzoul2@hotmail.com> wrote:
>
>> Buck wrote:
>> ::
>> :: Bill, you are showing your ignorance. Here are a few points:
>> ::
>>
>> Thanks for the info, Buck!
>>
>
> Only on Planet Baka. The funny part is Billy's follow up "excuse
> post."
Not really. 3 satellite CAN compute elevation but it needs a bit more
computing power than your average hand held device. Mathematically the
intersection of three spheres is two points and it takes just a little
more sts to know you are on the earth. A 4th satellite makes it
easier for a 'dumb' chip and does add another reference point for a
little more accuracy.
No excuse from me. I just got tired of arguing what should have been
mathematically obvious.
--
Bill (Sleepless biker) Baka
|
| |
Date: 26 Oct 2006 21:13:44
From: Nick Payne
Subject: Re: What bike computers measure elevation?
|
I've had good reliability from a Ciclosport CM436M, which contains
sufficient memory for 60hrs of recording at a 20sec sampling rate. It seems
completely waterproof, which was not the case with the Avocet 50 that I used
to have, and also comes with quite nice software for downloading data and
graphing rides. I have PDFs of a couple of rides downloaded from the unit at
http://www.users.on.net/~njpayne/bikestuff/Switzerland/RigiKulm.pdf and
http://www.users.on.net/~njpayne/bikestuff/Switzerland/Mostelegg.pdf.
Nick
"Harold Burton" <hal.i.burton@hotmail.com > wrote in message
news:hal.i.burton-6E424D.13410625102006@comcast.dca.giganews.com...
> I'm looking for a bike computer with a barometer that will give me the
> total climb on a ride. I had an old Cateye that did this but Cateye
> doesn't make such a beast any more. Any suggestions?
|
| | |
Date: 26 Oct 2006 06:19:42
From: Dan
Subject: Re: What bike computers measure elevation?
|
Nick Payne wrote:
> I've had good reliability from a Ciclosport CM436M, which contains
> sufficient memory for 60hrs of recording at a 20sec sampling rate. It
> seems completely waterproof, which was not the case with the Avocet 50
> that I used to have, and also comes with quite nice software for
> downloading data and graphing rides. I have PDFs of a couple of rides
> downloaded from the unit at
> http://www.users.on.net/~njpayne/bikestuff/Switzerland/RigiKulm.pdf and
> http://www.users.on.net/~njpayne/bikestuff/Switzerland/Mostelegg.pdf.
>
> Nick
>
> "Harold Burton" <hal.i.burton@hotmail.com> wrote in message
> news:hal.i.burton-6E424D.13410625102006@comcast.dca.giganews.com...
>> I'm looking for a bike computer with a barometer that will give me the
>> total climb on a ride. I had an old Cateye that did this but Cateye
>> doesn't make such a beast any more. Any suggestions?
>
I have the same computer. The data can also be loaded into EXCEL and
manipulated.
http://www.geocities.com/danmerrick/sonorapass2003/
|
| |
Date: 25 Oct 2006 21:43:51
From: Brian Huntley
Subject: Re: What bike computers measure elevation?
|
Dan wrote:
> For me, the best thing about a bike computer that recorded elevation is
> that I climbed a lot of hills to see what it would say.
*That* is nice and concise and probably very true for a lot of folks.
|
| |
Date: 25 Oct 2006 19:06:09
From: Dirtroadie
Subject: Re: What bike computers measure elevation?
|
jobst.brandt@stanfordalumni.org wrote:
> GPS does not give reasonable vertical resolution for bicycling.
Myth and Lore!
You have never used one, have you?
> Besides, collecting the cumulative elevation by most of the bicycle
> instruments is inaccurate because they add every groundswell within
> their resolution, thereby giving inflated estimates of climbing (or
> descending).
Wait just a minute. On the one hand your are saying that they have
insufficient resolution (untrue), yet on the other you are suggesting
that they are inaccurate because they measure every "groundswell" (I
assume you mean "variation in elvation"). It appears that you have
just contradicted yourself.
I recognize your contribution to the algorithm used in the ancient
Avocet instruments, but that hardly makes you an authority on GPS
especially when repeating such erroneous statements as your first one
above. And note for the record that along with improvement in GPS
devices, the system itself has greatly improved accuracy in this
century.
http://www.ngs.noaa.gov/FGCS/info/sans_SA/docs/statement.html
And recently the more accurate WAAS system (look it up) was made much
more useful within the continental USA by the repositioning of one of
the geostationary WAAS satellites so that it can be more readily "seen"
and used for the GPS corrections it provides.
See my earlier comments:
http://groups.google.com/group/rec.bicycles.tech/msg/38824a39ed8dedde?hl=en&
And check out software such as that available at topofusion.com to see
what GPS instruments are really capable of when their recorded data is
put to use.
DR
|
| | |
Date: 26 Oct 2006 02:39:58
From:
Subject: Re: What bike computers measure elevation?
|
someone snipes:
>> GPS does not give reasonable vertical resolution for bicycling.
> Myth and Lore! You have never used one, have you?
>> Besides, collecting the cumulative elevation by most of the bicycle
>> instruments is inaccurate because they add every groundswell within
>> their resolution, thereby giving inflated estimates of climbing (or
>> descending).
> Wait just a minute. On the one hand your are saying that they have
> insufficient resolution (untrue), yet on the other you are
> suggesting that they are inaccurate because they measure every
> "groundswell" (I assume you mean "variation in elvation"). It
> appears that you have just contradicted yourself.
I guess you don't understand what "within their resolution" means,
which doesn't get any better if that resolution is poor. It just
collects greater errors.
> I recognize your contribution to the algorithm used in the ancient
> Avocet instruments, but that hardly makes you an authority on GPS
> especially when repeating such erroneous statements as your first
> one above. And note for the record that along with improvement in
> GPS devices, the system itself has greatly improved accuracy in this
> century.
It's still not useful for bicycling altimeters.
http://www.ngs.noaa.gov/FGCS/info/sans_SA/docs/statement.html
> And recently the more accurate WAAS system (look it up) was made
> much more useful within the continental USA by the repositioning of
> one of the geostationary WAAS satellites so that it can be more
> readily "seen" and used for the GPS corrections it provides.
> See my earlier comments:
http://groups.google.com/group/rec.bicycles.tech/msg/38824a39ed8dedde?hl=en&
> And check out software such as that available at topofusion.com to see
> what GPS instruments are really capable of when their recorded data is
> put to use.
Which instrument do you suggest as a bicycle altimeter and speedometer/
odometer?
Jobst Brandt
|
| |
Date: 26 Oct 2006 00:09:24
From: Dennis Ferguson
Subject: Re: What bike computers measure elevation?
|
On 2006-10-25, Harold Burton <hal.i.burton@hotmail.com > wrote:
> I'm looking for a bike computer with a barometer that will give me the
> total climb on a ride. I had an old Cateye that did this but Cateye
> doesn't make such a beast any more. Any suggestions?
I have a Ciclosport CM434, like this:
http://tinyurl.com/yf6xuc
I like almost everything about it. It gives total climb numbers that
are fairly close to an Avocet 50, and the wireless sensor is well enough
done that passing an electric fence doesn't make it think I am riding at
200 mph (Polar sucks).
The only flaws I've noticed are that it costs too much, and that it
will add 8000 or 10000 feet to the total climb number when you take
it on an airplane flight (they shouldn't count elevation changes which
occur when the bike's speed is 0, or they should give you an off switch).
Oh, and some people complain about its configuration procedures, but I
don't find it worse than anything else.
Dennis Ferguson
|
| |
Date: 25 Oct 2006 16:46:40
From:
Subject: Re: What bike computers measure elevation?
|
Joe Riel wrote:
> bill <bbaka@c-o-m-c-a-s-t.net> writes:
>
> > jobst.brandt@stanfordalumni.org wrote:
> >> Bill Baka writes:
> >>
> >>>> I'm looking for a bike computer with a barometer that will give me
> >>>> the total climb on a ride. I had an old Cateye that did this but
> >>>> Cateye doesn't make such a beast any more. Any suggestions?
> >>
> >>> Anything with a GPS is capable of giving elevation since it will
> >>> resolve not only you latitude and longitude, but also you elevation.
> >>> This comes in handy for GPS enabled cell phones so the 911 operators
> >>> can tell not only where the address is you are calling from but also
> >>> what floor you are on. That might be more than you want to know,
> >>> but the stuff is out there if you want to pay for it.
> >> GPS does not give reasonable vertical resolution for bicycling.
> >> Besides, collecting the cumulative elevation by most of the bicycle
> >> instruments is inaccurate because they add every groundswell within
> >> their resolution, thereby giving inflated estimates of climbing (or
> >> descending).
> >> Jobst Brandt
> >
> > HUH?
> > You want more accurate than a few feet? Good luck.
>
> GPS elevation accuracy is not that good. It's more like +/-(15-20
> meters). Note that that is absolute accuracy. Doing hill repeats on
> a 200 meter vertical climb a Garmin Edge 205 gives the same elevation
> gain within a few meters.
That's a pretty big innaccuracy though... I think I've seen much better
response from my Foretrex 201 ... is it possible that the hill itself
or nearby hills came between you and one satellite?
|
| |
Date: 25 Oct 2006 22:51:05
From: Joe Riel
Subject: Re: What bike computers measure elevation?
|
bill <bbaka@c-o-m-c-a-s-t.net > writes:
> jobst.brandt@stanfordalumni.org wrote:
>> Bill Baka writes:
>>
>>>> I'm looking for a bike computer with a barometer that will give me
>>>> the total climb on a ride. I had an old Cateye that did this but
>>>> Cateye doesn't make such a beast any more. Any suggestions?
>>
>>> Anything with a GPS is capable of giving elevation since it will
>>> resolve not only you latitude and longitude, but also you elevation.
>>> This comes in handy for GPS enabled cell phones so the 911 operators
>>> can tell not only where the address is you are calling from but also
>>> what floor you are on. That might be more than you want to know,
>>> but the stuff is out there if you want to pay for it.
>> GPS does not give reasonable vertical resolution for bicycling.
>> Besides, collecting the cumulative elevation by most of the bicycle
>> instruments is inaccurate because they add every groundswell within
>> their resolution, thereby giving inflated estimates of climbing (or
>> descending).
>> Jobst Brandt
>
> HUH?
> You want more accurate than a few feet? Good luck.
GPS elevation accuracy is not that good. It's more like +/-(15-20
meters). Note that that is absolute accuracy. Doing hill repeats on
a 200 meter vertical climb a Garmin Edge 205 gives the same elevation
gain within a few meters.
--
Joe Riel
|
| |
Date: 25 Oct 2006 14:48:16
From: peter
Subject: Re: What bike computers measure elevation?
|
bill wrote:
> gds wrote:
> > Not all GPS units have the altitude feature. Although they are much
> > more common on newer models than on earlier ones.
Some of the new car-specific models may not, but I don't know of any
handheld GPS that's suitable for putting on a bicycle that doesn't have
some way of reporting altitude. All the older models that I know of
reported altitude. Some supplement the GPS-based altitude with a
barometric sensor for better stability and for situations where GPS
reception is lost, but even the most basic models report GPS-based
altitude.
> >
> The information is there for the taking since a GPS uses the
> triangulation of information from 3 satellites meaning you can be at one
> and only one point in space (hopefully on the Earth).
>
Actually, at least 4 satellites are required to determine altitude.
The GPS receiver solves for 4 unknowns (lat., long., altitude, and
time) and therefore needs data from 4 satellites. If only 3 are being
received then the receiver makes the assumption that the altitude is
still about the same as before and works out the best solution for the
other 3 variables.
|
| |
Date: 25 Oct 2006 13:04:49
From: gds
Subject: Re: What bike computers measure elevation?
|
bill wrote:
e. As I said "The data IS there". Whether you can use it is
> not my problem,
That is even sillier. Someone asks for advice and you give some, but it
is based on wrong information. Then you say it is someone elses
problem. Why bother to respond if you don't care if it's meaningful?
|
| | |
Date: 25 Oct 2006 20:20:18
From: bill
Subject: Re: What bike computers measure elevation?
|
gds wrote:
> bill wrote:
> e. As I said "The data IS there". Whether you can use it is
>> not my problem,
>
> That is even sillier. Someone asks for advice and you give some, but it
> is based on wrong information. Then you say it is someone elses
> problem. Why bother to respond if you don't care if it's meaningful?
>
I said the data is there and you can use it if you want to buy a decent
GPS enabled (insert whatever) device. That is neither silly nor
meaningless. A barometer can be very misleading if the weather changes
although it might tell you to go home if your altitude reading goes up
on a descent (storm coming at you fast).
--
Bill (Sleepless biker) Baka
|
| |
Date: 25 Oct 2006 15:03:52
From: Mike Enarson
Subject: Re: What bike computers measure elevation?
|
"Harold Burton" <hal.i.burton@hotmail.com > wrote in message
news:hal.i.burton-6E424D.13410625102006@comcast.dca.giganews.com...
> I'm looking for a bike computer with a barometer that will give me the
> total climb on a ride. I had an old Cateye that did this but Cateye
> doesn't make such a beast any more. Any suggestions?
I was checking out Blackburn on the web a couple days ago and I see that
their top of line cycle computer has this function. The Delphi 6.0 I think
it's model number was. The URL was:
http://www.delphicyclometers.com/home.html
You would probably have to find a Blackburn dealer for the price. I did not
even know they made computers.
Regards
Mike
|
| | |
Date: 25 Oct 2006 21:02:37
From: R Brickston
Subject: Re: What bike computers measure elevation?
|
On Wed, 25 Oct 2006 15:03:52 -0500, "Mike Enarson" <menarson@cox.net >
wrote:
>"Harold Burton" <hal.i.burton@hotmail.com> wrote in message
>news:hal.i.burton-6E424D.13410625102006@comcast.dca.giganews.com...
>> I'm looking for a bike computer with a barometer that will give me the
>> total climb on a ride. I had an old Cateye that did this but Cateye
>> doesn't make such a beast any more. Any suggestions?
>
>I was checking out Blackburn on the web a couple days ago and I see that
>their top of line cycle computer has this function. The Delphi 6.0 I think
>it's model number was. The URL was:
>http://www.delphicyclometers.com/home.html
>
>You would probably have to find a Blackburn dealer for the price. I did not
>even know they made computers.
>
>Regards
>Mike
>
$140 on Amazon. Has percentage grade function also.
|
| |
Date: 25 Oct 2006 11:37:25
From: gds
Subject: Re: What bike computers measure elevation?
|
bill wrote:
> gds wrote:
> > bill wrote:
> >> Harold Burton wrote:
> >>> I'm looking for a bike computer with a barometer that will give me the
> >>> total climb on a ride. I had an old Cateye that did this but Cateye
> >>> doesn't make such a beast any more. Any suggestions?
> >> Anything with a GPS is capable of giving elevation since it will resolve
> >> not only you latitude and longitude, but also you elevation. This comes
> >> in handy for GPS enabled cell phones so the 911 operators can tell not
> >> only where the address is you are calling from but also what floor you
> >> are on. That might be more than you want to know, but the stuff is out
> >> there if you want to pay for it.
> >>
> >> --
> >> Bill (Sleepless biker) Baka
> > Not all GPS units have the altitude feature. Although they are much
> > more common on newer models than on earlier ones.
> >
> The information is there for the taking since a GPS uses the
> triangulation of information from 3 satellites meaning you can be at one
> and only one point in space (hopefully on the Earth).
>
> --
> Bill (Sleepless biker) Baka
That is a silly reply. If the GPS unit has no altitude read out -and
not all do- then it makes no difference that the data is "there for the
taking" as there is no way to "take it."
|
| | |
Date: 25 Oct 2006 18:43:52
From: bill
Subject: Re: What bike computers measure elevation?
|
gds wrote:
> bill wrote:
>> gds wrote:
>>> bill wrote:
>>>> Harold Burton wrote:
>>>>> I'm looking for a bike computer with a barometer that will give me the
>>>>> total climb on a ride. I had an old Cateye that did this but Cateye
>>>>> doesn't make such a beast any more. Any suggestions?
>>>> Anything with a GPS is capable of giving elevation since it will resolve
>>>> not only you latitude and longitude, but also you elevation. This comes
>>>> in handy for GPS enabled cell phones so the 911 operators can tell not
>>>> only where the address is you are calling from but also what floor you
>>>> are on. That might be more than you want to know, but the stuff is out
>>>> there if you want to pay for it.
>>>>
>>>> --
>>>> Bill (Sleepless biker) Baka
>>> Not all GPS units have the altitude feature. Although they are much
>>> more common on newer models than on earlier ones.
>>>
>> The information is there for the taking since a GPS uses the
>> triangulation of information from 3 satellites meaning you can be at one
>> and only one point in space (hopefully on the Earth).
>>
>> --
>> Bill (Sleepless biker) Baka
>
> That is a silly reply. If the GPS unit has no altitude read out -and
> not all do- then it makes no difference that the data is "there for the
> taking" as there is no way to "take it."
>
Ask a 911 operator who gets an emergency call from someone in a high
rise and does not know what floor they are on. The newer GPS enabled
phones are supposed to give them that information. Whether you can
access it yourself is another can of worms since I don't own one and
don't want one. As I said "The data IS there". Whether you can use it is
not my problem, just depends on how much you want to spend. A friend had
a Radio Shack unit that gave elevation back in 2001, and it only cost
him about $100 the so they should be cheaper now.
--
Bill (Sleepless biker) Baka
|
| | | |
Date: 25 Oct 2006 21:46:35
From: Solvang Cyclist
Subject: Re: What bike computers measure elevation?
|
bill <bbaka@c-o-m-c-a-s-t.net > wrote in news:IfO%g.15997$GR.1026
@newssvr29.news.prodigy.net:
> Ask a 911 operator who gets an emergency call from someone in a high
> rise and does not know what floor they are on. The newer GPS enabled
> phones are supposed to give them that information.
I don't believe this is true. Even the newer GPS receivers have VERY POOR
vertical accuracy. Even if the vertical accuracy was as good as the
horizontal, that's only about 30 feet. Great for finding you on the
ground, but +/- 30 feet would be a range of 7 floors of a typical
building. As I recall, the current requirements for Mobile E911 (Enhanced
911) service - which has been delayed several times - is on the order of
several hundred feet in the horizontal and no requirements for altitude
information.
Also, it actually takes 4 not 3 satellites to get a location. That's
because the system is "triangulating" in three dimensions - not just two.
Cheers,
David
|
| | | | |
Date: 26 Oct 2006 09:42:43
From: bill
Subject: Re: What bike computers measure elevation?
|
Solvang Cyclist wrote:
> bill <bbaka@c-o-m-c-a-s-t.net> wrote in news:IfO%g.15997$GR.1026
> @newssvr29.news.prodigy.net:
>
>> Ask a 911 operator who gets an emergency call from someone in a high
>> rise and does not know what floor they are on. The newer GPS enabled
>> phones are supposed to give them that information.
>
> I don't believe this is true. Even the newer GPS receivers have VERY POOR
> vertical accuracy. Even if the vertical accuracy was as good as the
> horizontal, that's only about 30 feet. Great for finding you on the
> ground, but +/- 30 feet would be a range of 7 floors of a typical
> building. As I recall, the current requirements for Mobile E911 (Enhanced
> 911) service - which has been delayed several times - is on the order of
> several hundred feet in the horizontal and no requirements for altitude
> information.
>
> Also, it actually takes 4 not 3 satellites to get a location. That's
> because the system is "triangulating" in three dimensions - not just two.
>
> Cheers,
> David
>
The intersection of 2 spheres is a big circle. 3 spheres gives you 2
points, one on the surface of the earth, and one either inside the earth
or out in space. 4 would eliminate that last ambiguity but realistically
how would you go from on a bike to 400 or so miles out in space in the
blink of an eye. The vertical accuracy is just as good as the latitude
and longitude, so if there is any limitation, it is either the
instrument vendor not taking it seriously or the government putting a
limit on it. There used to be a military mandated block on x-y accuracy
for consumers until about 5 years ago when 911 operators started wanting
it to locate accident (and lost) victims. The electronics is capable of
about 3 feet (nanoseconds) so a 7 floor range strikes me as ridiculous.
--
Bill (Sleepless biker) Baka
|
| |
Date: 25 Oct 2006 11:36:21
From: gds
Subject: Re: What bike computers measure elevation?
|
bill wrote:
> gds wrote:
> > bill wrote:
> >> Harold Burton wrote:
> >>> I'm looking for a bike computer with a barometer that will give me the
> >>> total climb on a ride. I had an old Cateye that did this but Cateye
> >>> doesn't make such a beast any more. Any suggestions?
> >> Anything with a GPS is capable of giving elevation since it will resolve
> >> not only you latitude and longitude, but also you elevation. This comes
> >> in handy for GPS enabled cell phones so the 911 operators can tell not
> >> only where the address is you are calling from but also what floor you
> >> are on. That might be more than you want to know, but the stuff is out
> >> there if you want to pay for it.
> >>
> >> --
> >> Bill (Sleepless biker) Baka
> > Not all GPS units have the altitude feature. Although they are much
> > more common on newer models than on earlier ones.
> >
> The information is there for the taking since a GPS uses the
> triangulation of information from 3 satellites meaning you can be at one
> and only one point in space (hopefully on the Earth).
>
> --
> Bill (Sleepless biker) Baka
|
| |
Date: 25 Oct 2006 11:25:32
From: bfd
Subject: Re: What bike computers measure elevation?
|
Harold Burton wrote:
> I'm looking for a bike computer with a barometer that will give me the
> total climb on a ride. I had an old Cateye that did this but Cateye
> doesn't make such a beast any more. Any suggestions?
Does Avocet still sell its Model 50 "altimeter" computer?
|
| |
Date: 25 Oct 2006 11:12:13
From: Dan
Subject: Re: What bike computers measure elevation?
|
Harold Burton wrote:
> I'm looking for a bike computer with a barometer that will give me the
> total climb on a ride. I had an old Cateye that did this but Cateye
> doesn't make such a beast any more. Any suggestions?
Not really a bike computer but a GPS unit like the Garmin 201 can be had
for less than $150. It will display speed and distance. The data can be
loaded into a computer and overlaid on maps or analyzed for stats such
as elevation gain. I like mine.
http://www.shop.com/op/~201_FORERUNNER_PERSONAL-prod-33764520-44177947?sourceid=298
I have had a Ciclosport 434M for about 4 years and it has worked fine.
It can transfer data to your PC (the software is a bit clunky but
adequate). They can still be had for $170 (much less than I paid):
http://www.coloradocyclist.com/common/products/productdisplay2.cfm?PRRFNBR=29599
For a few dollars less you can get the non-PC version:
http://www.performancebike.com/shop/profile.cfm?SKU=17151&srccode=2228&PID=484346
I also have an Oregon Scientific Sport watch/bike computer with
altimeter, HR, cadence, etc. but I have never used it. It also connects
to the PC:
http://www.digitalgiftstore.com/rp107-000box.html
I don't have the box anymore but would be happy to let anybody have it
for $100 plus say $20 to box it up and post it (in the US).
|
| | |
Date: 25 Oct 2006 11:37:52
From: Dan
Subject: Re: What bike computers measure elevation?
|
Dan wrote:
> I also have an Oregon Scientific Sport watch/bike computer with
> altimeter, HR, cadence, etc. but I have never used it. It also connects
> to the PC:
> http://www.digitalgiftstore.com/rp107-000box.html
>
> I don't have the box anymore but would be happy to let anybody have it
> for $100 plus say $20 to box it up and post it (in the US).
actually, I see much cheaper:
http://tinyurl.com/y9f4jg
|
| |
Date: 25 Oct 2006 11:09:03
From: gds
Subject: Re: What bike computers measure elevation?
|
bill wrote:
> Harold Burton wrote:
> > I'm looking for a bike computer with a barometer that will give me the
> > total climb on a ride. I had an old Cateye that did this but Cateye
> > doesn't make such a beast any more. Any suggestions?
>
> Anything with a GPS is capable of giving elevation since it will resolve
> not only you latitude and longitude, but also you elevation. This comes
> in handy for GPS enabled cell phones so the 911 operators can tell not
> only where the address is you are calling from but also what floor you
> are on. That might be more than you want to know, but the stuff is out
> there if you want to pay for it.
>
> --
> Bill (Sleepless biker) Baka
Not all GPS units have the altitude feature. Although they are much
more common on newer models than on earlier ones.
|
| | |
Date: 25 Oct 2006 18:29:10
From: bill
Subject: Re: What bike computers measure elevation?
|
gds wrote:
> bill wrote:
>> Harold Burton wrote:
>>> I'm looking for a bike computer with a barometer that will give me the
>>> total climb on a ride. I had an old Cateye that did this but Cateye
>>> doesn't make such a beast any more. Any suggestions?
>> Anything with a GPS is capable of giving elevation since it will resolve
>> not only you latitude and longitude, but also you elevation. This comes
>> in handy for GPS enabled cell phones so the 911 operators can tell not
>> only where the address is you are calling from but also what floor you
>> are on. That might be more than you want to know, but the stuff is out
>> there if you want to pay for it.
>>
>> --
>> Bill (Sleepless biker) Baka
> Not all GPS units have the altitude feature. Although they are much
> more common on newer models than on earlier ones.
>
The information is there for the taking since a GPS uses the
triangulation of information from 3 satellites meaning you can be at one
and only one point in space (hopefully on the Earth).
--
Bill (Sleepless biker) Baka
|
| | | |
Date: 25 Oct 2006 19:21:43
From: Booker C. Bense
Subject: Re: What bike computers measure elevation?
|
-----BEGIN PGP SIGNED MESSAGE-----
In article <W1O%g.15990$GR.9136@newssvr29.news.prodigy.net >,
bill <"just use comcast", "you know the drill for no spam bots." > wrote:
>>
>The information is there for the taking since a GPS uses the
>triangulation of information from 3 satellites meaning you can be at one
>and only one point in space (hopefully on the Earth).
The GPS's that display altitude generally
use a internal barometer to do it. It is only very recently
with the addition of WAAS signal that GPS can have any
reasonable accuracy wrt altitude. Even then most GPS's can
not approach the accuracy of a recently calibrated barometer.
GPS does not work by triangulation, but by time codes to calculate
distance, you know how far you are from the satellite, not what
angle. It takes a minimum of 4 satellites to determine a
position and the more satellites available the more accurate
the positioning data. I suggest a quick read of Wikipedia's
GPS article.
If you want altitude data, the Garmin Edge 205/305 is a very nice if
pricy cyclometer.
http://www.garmin.com/products/edge305/
_ Booker C. Bense
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-----END PGP SIGNATURE-----
|
| | | | |
Date: 25 Oct 2006 20:00:01
From: bill
Subject: Re: What bike computers measure elevation?
|
Booker C. Bense wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
>
> In article <W1O%g.15990$GR.9136@newssvr29.news.prodigy.net>,
> bill <"just use comcast", "you know the drill for no spam bots."> wrote:
>> The information is there for the taking since a GPS uses the
>> triangulation of information from 3 satellites meaning you can be at one
>> and only one point in space (hopefully on the Earth).
>
> The GPS's that display altitude generally
> use a internal barometer to do it. It is only very recently
> with the addition of WAAS signal that GPS can have any
> reasonable accuracy wrt altitude. Even then most GPS's can
> not approach the accuracy of a recently calibrated barometer.
>
> GPS does not work by triangulation, but by time codes to calculate
> distance, you know how far you are from the satellite, not what
> angle. It takes a minimum of 4 satellites to determine a
> position and the more satellites available the more accurate
> the positioning data. I suggest a quick read of Wikipedia's
> GPS article.
You totally don't understand GPS I take it. It uses a highly accurate
time signal from no less than 3 satellites and calculates your position
in 3 dimensions, period. I suggest you go to NASA or JPL's site and look
at the real information. Wikipedia's data is not all that reliable since
it is a public domain work in progress and good data can be overwritten
with bad if someone doesn't know what they are posting to it.
GPS can be represented by three spheres surrounding three satellites.
There can be 2 points of intersection but one would put you either
inside the Earth or hundreds of miles out in space, so it isn't rocket
science to figure it out.
>
> If you want altitude data, the Garmin Edge 205/305 is a very nice if
> pricy cyclometer.
>
> http://www.garmin.com/products/edge305/
>
>
> _ Booker C. Bense
>
> -----BEGIN PGP SIGNATURE-----
> Version: 2.6.2
>
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> -----END PGP SIGNATURE-----
--
Bill (Sleepless biker) Baka
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| | | | | |
Date: 25 Oct 2006 21:53:05
From: Solvang Cyclist
Subject: Re: What bike computers measure elevation?
|
bill <bbaka@c-o-m-c-a-s-t.net > wrote in news:5nP%g.15941$TV3.5574
@newssvr21.news.prodigy.com:
> You totally don't understand GPS I take it. It uses a highly accurate
> time signal from no less than 3 satellites and calculates your position
> in 3 dimensions, period.
I'm afraid it's a bit more complex than you indicate. Since figuring out
the distance to each satellite requires the receiver to know exactly what
time it is, but it only knows what time it is based on the signals that
reach it from the satellites and knowing how long it took for the signal to
get to the receiver - you have a bit of a catch-22. In order to resolve
this a 4th satellite is required.
Regardless, the ability to determine what floor of a building you are on
using a consumer GPS is just not there.
David
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| | | | | | |
Date: 26 Oct 2006 09:47:12
From: bill
Subject: Re: What bike computers measure elevation?
|
Solvang Cyclist wrote:
> bill <bbaka@c-o-m-c-a-s-t.net> wrote in news:5nP%g.15941$TV3.5574
> @newssvr21.news.prodigy.com:
>
>> You totally don't understand GPS I take it. It uses a highly accurate
>> time signal from no less than 3 satellites and calculates your position
>> in 3 dimensions, period.
>
> I'm afraid it's a bit more complex than you indicate. Since figuring out
> the distance to each satellite requires the receiver to know exactly what
> time it is, but it only knows what time it is based on the signals that
> reach it from the satellites and knowing how long it took for the signal to
> get to the receiver - you have a bit of a catch-22. In order to resolve
> this a 4th satellite is required.
The satellites used highly stable time sources and are synced with WWV,
and yes, there often is a 4th satellite is range, not necessarily used,
but there.
>
> Regardless, the ability to determine what floor of a building you are on
> using a consumer GPS is just not there.
You said the word, consumer, but as more cell phones get GPS abilities
and 911 wants better locating service it will come. The cost to the
phone makers will be about a nickel. The cost passed to consumers will
probably be about 20-50 dollars more pure profit.
>
> David
--
Bill (Sleepless biker) Baka
|
| |
Date: 25 Oct 2006 14:04:16
From: H. Guy
Subject: Re: What bike computers measure elevation?
|
In article <hal.i.burton-6E424D.13410625102006@comcast.dca.giganews.com >,
Harold Burton <hal.i.burton@hotmail.com > wrote:
> I'm looking for a bike computer with a barometer that will give me the
> total climb on a ride. I had an old Cateye that did this but Cateye
> doesn't make such a beast any more. Any suggestions?
VDO's lovely & expensive MC 1.0 will do this. they even make a
wireless model.
|
| |
Date: 25 Oct 2006 18:03:28
From: bill
Subject: Re: What bike computers measure elevation?
|
Harold Burton wrote:
> I'm looking for a bike computer with a barometer that will give me the
> total climb on a ride. I had an old Cateye that did this but Cateye
> doesn't make such a beast any more. Any suggestions?
Anything with a GPS is capable of giving elevation since it will resolve
not only you latitude and longitude, but also you elevation. This comes
in handy for GPS enabled cell phones so the 911 operators can tell not
only where the address is you are calling from but also what floor you
are on. That might be more than you want to know, but the stuff is out
there if you want to pay for it.
--
Bill (Sleepless biker) Baka
|
| | |
Date: 27 Oct 2006 18:26:58
From: peter
Subject: Re: What bike computers measure elevation?
|
bill wrote:
> peter wrote:
> > bill wrote:
> >
> >> Not really. 3 satellite CAN compute elevation but it needs a bit more
> >> computing power than your average hand held device.
> >
> > No, computing power is not the problem. You could have the processor
> > of a supercomputer and still wouldn't be able to solve for 4 variables
> > (lat., long., elevation, and time) using only three pieces of data.
> > Now if your GPS receiver had its own atomic clock built in that was
> > synchronized with those of the satellites then it wouldn't need to
> > solve for time and reception of three satellite signals would be
> > sufficient. But it's much more practical to make do without the atomic
> > clock in the receiver and instead rely on getting signals from a fourth
> > satellite.
> >
> > See:
> > http://www.trimble.com/gps/howgps-timing2.shtml
> > for more details.
> >
> I think I mentioned time in a post that mentioned a Cesium reference is
> just a bit BIG to be in a hand held device.
Yes, but then you went back to claiming what you did above; i.e. that
receiving 3 satellite signals would be sufficient if you just had a
decent processor - that's not true.
BTW, the actual atomic clock hardware can be quite small:
http://physicsweb.org/articles/news/8/9/2/1
but of course you need some associated electronics
|
| | | |
Date: 28 Oct 2006 05:21:38
From: bill
Subject: Re: What bike computers measure elevation?
|
peter wrote:
> bill wrote:
>> peter wrote:
>>> bill wrote:
>>>
>>>> Not really. 3 satellite CAN compute elevation but it needs a bit more
>>>> computing power than your average hand held device.
>>> No, computing power is not the problem. You could have the processor
>>> of a supercomputer and still wouldn't be able to solve for 4 variables
>>> (lat., long., elevation, and time) using only three pieces of data.
>>> Now if your GPS receiver had its own atomic clock built in that was
>>> synchronized with those of the satellites then it wouldn't need to
>>> solve for time and reception of three satellite signals would be
>>> sufficient. But it's much more practical to make do without the atomic
>>> clock in the receiver and instead rely on getting signals from a fourth
>>> satellite.
>>>
>>> See:
>>> http://www.trimble.com/gps/howgps-timing2.shtml
>>> for more details.
>>>
>> I think I mentioned time in a post that mentioned a Cesium reference is
>> just a bit BIG to be in a hand held device.
>
> Yes, but then you went back to claiming what you did above; i.e. that
> receiving 3 satellite signals would be sufficient if you just had a
> decent processor - that's not true.
>
> BTW, the actual atomic clock hardware can be quite small:
> http://physicsweb.org/articles/news/8/9/2/1
> but of course you need some associated electronics
>
I remember reading about that in one of my electronics magazines about a
week ago. It is something like thousands of times better than a quartz
crystal but thousands of time worse that the big NIST Cesium bank, which
has multiple oscillators averaged. Geesh, If my watch only lost a second
every 30 million years I think I would be happy, but every 300 years and
I might complain. The article mentions that they 'could' be incorporated
in consumer equipment! Any bets on the price?
--
Bill (Sleepless biker) Baka
|
| | |
Date: 27 Oct 2006 15:33:14
From: peter
Subject: Re: What bike computers measure elevation?
|
bill wrote:
> Not really. 3 satellite CAN compute elevation but it needs a bit more
> computing power than your average hand held device.
No, computing power is not the problem. You could have the processor
of a supercomputer and still wouldn't be able to solve for 4 variables
(lat., long., elevation, and time) using only three pieces of data.
Now if your GPS receiver had its own atomic clock built in that was
synchronized with those of the satellites then it wouldn't need to
solve for time and reception of three satellite signals would be
sufficient. But it's much more practical to make do without the atomic
clock in the receiver and instead rely on getting signals from a fourth
satellite.
See:
http://www.trimble.com/gps/howgps-timing2.shtml
for more details.
|
| | | |
Date: 28 Oct 2006 00:21:31
From: bill
Subject: Re: What bike computers measure elevation?
|
peter wrote:
> bill wrote:
>
>> Not really. 3 satellite CAN compute elevation but it needs a bit more
>> computing power than your average hand held device.
>
> No, computing power is not the problem. You could have the processor
> of a supercomputer and still wouldn't be able to solve for 4 variables
> (lat., long., elevation, and time) using only three pieces of data.
> Now if your GPS receiver had its own atomic clock built in that was
> synchronized with those of the satellites then it wouldn't need to
> solve for time and reception of three satellite signals would be
> sufficient. But it's much more practical to make do without the atomic
> clock in the receiver and instead rely on getting signals from a fourth
> satellite.
>
> See:
> http://www.trimble.com/gps/howgps-timing2.shtml
> for more details.
>
I think I mentioned time in a post that mentioned a Cesium reference is
just a bit BIG to be in a hand held device.
--
Bill (Sleepless biker) Baka
|
| | |
Date: 25 Oct 2006 19:56:37
From:
Subject: Re: What bike computers measure elevation?
|
Bill Baka writes:
>> I'm looking for a bike computer with a barometer that will give me
>> the total climb on a ride. I had an old Cateye that did this but
>> Cateye doesn't make such a beast any more. Any suggestions?
> Anything with a GPS is capable of giving elevation since it will
> resolve not only you latitude and longitude, but also you elevation.
> This comes in handy for GPS enabled cell phones so the 911 operators
> can tell not only where the address is you are calling from but also
> what floor you are on. That might be more than you want to know,
> but the stuff is out there if you want to pay for it.
GPS does not give reasonable vertical resolution for bicycling.
Besides, collecting the cumulative elevation by most of the bicycle
instruments is inaccurate because they add every groundswell within
their resolution, thereby giving inflated estimates of climbing (or
descending).
Jobst Brandt
|
| | | |
Date: 26 Oct 2006 18:00:12
From: Harold Burton
Subject: Re: What bike computers measure elevation?
|
In article <453fc175$0$34573$742ec2ed@news.sonic.net >,
jobst.brandt@stanfordalumni.org wrote:
> Bill Baka writes:
>
> >> I'm looking for a bike computer with a barometer that will give me
> >> the total climb on a ride. I had an old Cateye that did this but
> >> Cateye doesn't make such a beast any more. Any suggestions?
>
> > Anything with a GPS is capable of giving elevation since it will
> > resolve not only you latitude and longitude, but also you elevation.
> > This comes in handy for GPS enabled cell phones so the 911 operators
> > can tell not only where the address is you are calling from but also
> > what floor you are on. That might be more than you want to know,
> > but the stuff is out there if you want to pay for it.
>
> GPS does not give reasonable vertical resolution for bicycling.
That's for sure. I have a Garmin Etrex Legend that I use for kayaking.
I stay within a couple of feet of sea level but the elevation profile it
spits out shows variations of 40 feet or more.
|
| | | | |
Date: 27 Oct 2006 18:38:40
From: Lou Holtman
Subject: Re: What bike computers measure elevation?
|
Harold Burton wrote:
> In article <453fc175$0$34573$742ec2ed@news.sonic.net>,
> jobst.brandt@stanfordalumni.org wrote:
>
>
>>Bill Baka writes:
>>
>>
>>>>I'm looking for a bike computer with a barometer that will give me
>>>>the total climb on a ride. I had an old Cateye that did this but
>>>>Cateye doesn't make such a beast any more. Any suggestions?
>>
>>>Anything with a GPS is capable of giving elevation since it will
>>>resolve not only you latitude and longitude, but also you elevation.
>>>This comes in handy for GPS enabled cell phones so the 911 operators
>>>can tell not only where the address is you are calling from but also
>>>what floor you are on. That might be more than you want to know,
>>>but the stuff is out there if you want to pay for it.
>>
>>GPS does not give reasonable vertical resolution for bicycling.
>
>
>
>
>
> That's for sure. I have a Garmin Etrex Legend that I use for kayaking.
> I stay within a couple of feet of sea level but the elevation profile it
> spits out shows variations of 40 feet or more.
And you think 40 feet is bad? I always have to smile when people say: 'I
climbed the Galibier today and my altitude (GPS or barometric) meter
said 2610 meters instead of the promised 2642 meters'.....
Lou
--
Posted by news://news.nb.nu
|
| | | | |
Date: 26 Oct 2006 22:04:32
From: bill
Subject: Re: What bike computers measure elevation?
|
Harold Burton wrote:
> In article <453fc175$0$34573$742ec2ed@news.sonic.net>,
> jobst.brandt@stanfordalumni.org wrote:
>
>> Bill Baka writes:
>>
>>>> I'm looking for a bike computer with a barometer that will give me
>>>> the total climb on a ride. I had an old Cateye that did this but
>>>> Cateye doesn't make such a beast any more. Any suggestions?
>>> Anything with a GPS is capable of giving elevation since it will
>>> resolve not only you latitude and longitude, but also you elevation.
>>> This comes in handy for GPS enabled cell phones so the 911 operators
>>> can tell not only where the address is you are calling from but also
>>> what floor you are on. That might be more than you want to know,
>>> but the stuff is out there if you want to pay for it.
>> GPS does not give reasonable vertical resolution for bicycling.
>
>
>
>
> That's for sure. I have a Garmin Etrex Legend that I use for kayaking.
> I stay within a couple of feet of sea level but the elevation profile it
> spits out shows variations of 40 feet or more.
Are you going between mountains that can block a satellite or cause
multipath problems? It can guess with 3 birds in sight but needs 4 for a
really accurate fix. I suspect the military is happy with it the way it
is just to send the st bombs down at x-y and not worry about z (alt).
--
Bill (Sleepless biker) Baka
|
| | | |
Date: 25 Oct 2006 14:34:22
From: Dan
Subject: Re: What bike computers measure elevation?
|
jobst.brandt@stanfordalumni.org wrote:
>
> GPS does not give reasonable vertical resolution for bicycling.
I think GPS can actually determine elevation with adequate accuracy for
most cyclists these days. I have carried a bike computer with barometric
altimeter and a GPS unit at the same time in order to compare the two.
In some ways the GPS may be better since it isn't effected by
non-elevation pressure changes. Also, the barometric units can register
elevation changes as air speed changes due (I guess) to Bernoulli's
theorem. I have watched the displayed elevation on mine jump up and down
on a flat ride with a gusty head wind.
> Besides, collecting the cumulative elevation by most of the bicycle
> instruments is inaccurate because they add every groundswell within
> their resolution, thereby giving inflated estimates of climbing (or
> descending).
We would have to agree on what accurate means before I agree with this.
So long as one knows what is being measured and how, it doesn't matter
too much. On relatively flat terrain the error can be huge but who cares
about total climb on flat terrain? As far as I can tell, barometric
units work well enough on a steady climb of fair steepness. None of us
can agree on how to quantify things like slope and total climb anyway
(how high does a bump have to be to count? Should we count a 100 ft
climb in 1/10 mile and disregard a steady 100 ft climb in 10 miles?).
Whatever method a computer uses to measure total climb, it can still be
useful for qualitative comparison with other records by the same method.
If I am really interested in the data, I will usually load it into the
PC and filter or process it in some way. With USGS topographical maps
available on line these days, it is easy to check elevations too.
>
> Jobst Brandt
For me, the best thing about a bike computer that recorded elevation is
that I climbed a lot of hills to see what it would say.
Dan Merrick
|
| | | | |
Date: 25 Oct 2006 22:06:18
From:
Subject: Re: What bike computers measure elevation?
|
Dan Merrick writes:
>> GPS does not give reasonable vertical resolution for bicycling.
> I think GPS can actually determine elevation with adequate accuracy
> for most cyclists these days. I have carried a bike computer with
> barometric altimeter and a GPS unit at the same time in order to
> compare the two. In some ways the GPS may be better since it isn't
> effected by non-elevation pressure changes. Also, the barometric
> units can register elevation changes as air speed changes due (I
> guess) to Bernoulli's theorem. I have watched the displayed
> elevation on mine jump up and down on a flat ride with a gusty head
> wind.
I don't know what instrument you have but the old AVO50 doesn't do
that, mainly because it has a sampling rate that averages over a
reasonable time that cancels any such excursions.
>> Besides, collecting the cumulative elevation by most of the bicycle
>> instruments is inaccurate because they add every groundswell within
>> their resolution, thereby giving inflated estimates of climbing (or
>> descending).
> We would have to agree on what accurate means before I agree with
> this. So long as one knows what is being measured and how, it
> doesn't matter too much. On relatively flat terrain the error can
> be huge but who cares about total climb on flat terrain? As far as
> I can tell, barometric units work well enough on a steady climb of
> fair steepness.
All rides of interest have flat spots RR over/under passes and rollers
for which one doesn't shift but takes in stride. It was these changes
in elevation that are not counted by means of a logical hysteresis in
the AVO50. Therefore, all major elevation gains (for instance) are
counted so that compared with other instruments used on the same ride,
give a total that more accurately represents what was done.
> None of us can agree on how to quantify things like slope and total
> climb anyway (how high does a bump have to be to count?
...large enough that one feels the need for shifting and slowing from
the flatland pace. This is a bit more than most RR underpasses.
That's how the 10m criterion was arrived upon.
> Should we count a 100 ft climb in 1/10 mile and disregard a steady
> 100 ft climb in 10 miles?). Whatever method a computer uses to
> measure total climb, it can still be useful for qualitative
> comparison with other records by the same method. If I am really
> interested in the data, I will usually load it into the PC and
> filter or process it in some way. With USGS topographical maps
> available on line these days, it is easy to check elevations too.
The criterion is more than 10m from the last lowest point, which
becomes the datum of upward climb. A new datum is set if a descent of
more than 10m is encountered.
> For me, the best thing about a bike computer that recorded elevation
> is that I climbed a lot of hills to see what it would say.
That doesn't help the tourist who wants to know what to expect when
riding a certain route. You can assess that in a ride report that
contains good elevation information:
http://www.bicyclinglife.com/Recreation/SierraSpring.htm
Jobst Brandt
|
| | | |
Date: 25 Oct 2006 20:14:46
From: bill
Subject: Re: What bike computers measure elevation?
|
jobst.brandt@stanfordalumni.org wrote:
> Bill Baka writes:
>
>>> I'm looking for a bike computer with a barometer that will give me
>>> the total climb on a ride. I had an old Cateye that did this but
>>> Cateye doesn't make such a beast any more. Any suggestions?
>
>> Anything with a GPS is capable of giving elevation since it will
>> resolve not only you latitude and longitude, but also you elevation.
>> This comes in handy for GPS enabled cell phones so the 911 operators
>> can tell not only where the address is you are calling from but also
>> what floor you are on. That might be more than you want to know,
>> but the stuff is out there if you want to pay for it.
>
> GPS does not give reasonable vertical resolution for bicycling.
> Besides, collecting the cumulative elevation by most of the bicycle
> instruments is inaccurate because they add every groundswell within
> their resolution, thereby giving inflated estimates of climbing (or
> descending).
>
> Jobst Brandt
HUH?
You want more accurate than a few feet? Good luck. If you want to go
overboard I could suggest lugging around a laptop and hooking it into
the GPS via USB, wireless (bluetooth, zigbee, 802.11,b,g or whatever and
then you could profile and analyze the snot out of an entire trip. Who
besides a pro would want to do that?
--
Bill (Sleepless biker) Baka
|
| |
Date: 25 Oct 2006 13:49:58
From: Roger Zoul
Subject: Re: What bike computers measure elevation?
|
Harold Burton wrote:
:: I'm looking for a bike computer with a barometer that will give me
:: the total climb on a ride. I had an old Cateye that did this but
:: Cateye doesn't make such a beast any more. Any suggestions?
the polar 720i does it, though there must be less expensive ones that do
this also.
|
|
