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Old 06-06-07, 06:27 AM   #1
nickf829
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Altimeter and Cadence in a computer?

I'm looking for a decent computer to put on my bike. I'm interested in seeing gradient, feet climbed and cadence. Is there anything on the market other than the Garmin 305 that does both of these? Are the altimeter readings accurate on these or are they usually just ballpark figures
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Old 06-06-07, 06:29 AM   #2
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Polar CS600. It uses a barometric altimeter which is extremely precise in terms of measuring elevation gain, etc. but not very accurate in terms of altitude numbers unless you calibrate it every ride.
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Old 06-06-07, 07:28 AM   #3
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An alitimeter uses barometric pressure and so it is dependent on the weather. The same spot could change 100 ft in a day. And the only way to get better altimeter readings is to either calibrate it every ride or use a GPS altimeter, which does not rely on a barometer.
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Old 06-06-07, 07:31 AM   #4
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Blackburn Delphi 6.0. Barometric altimeter.
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Old 06-06-07, 07:39 AM   #5
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Quote:
Originally Posted by DrPete
Polar CS600. It uses a barometric altimeter which is extremely precise in terms of measuring elevation gain, etc. but not very accurate in terms of altitude numbers unless you calibrate it every ride.
Even then, weather changes on the ride and so do the barometric environment. I suspect you really need a barometric altimeter with GPS co-calibration to get dependable numbers.
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Old 06-06-07, 07:42 AM   #6
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Quote:
Originally Posted by lvleph
An alitimeter uses barometric pressure and so it is dependent on the weather. The same spot could change 100 ft in a day. And the only way to get better altimeter readings is to either calibrate it every ride or use a GPS altimeter, which does not rely on a barometer.
Actually, Garmin's GPS units also depend on barometric altimeter but gets real time comparison with its GPS data. GPS altimeter aren't as sensitive and can have large fluctuations when there are reception issues.
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Old 06-06-07, 07:53 AM   #7
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Originally Posted by sogood
Actually, Garmin's GPS units also depend on barometric altimeter but gets real time comparison with its GPS data. GPS altimeter aren't as sensitive and can have large fluctuations when there are reception issues.
Or when the military limits its accuracy.
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Old 06-06-07, 07:54 AM   #8
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Quote:
Originally Posted by lvleph
Or when the military limits its accuracy.
Unless you plan on doing a lot of riding in Afghanistan this won't really be a major concern.
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Old 06-06-07, 08:06 AM   #9
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Vetta makes (or at least made) their V100A which could have both altimeter and cadence information.
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Old 06-06-07, 08:09 AM   #10
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Originally Posted by DrPete
Unless you plan on doing a lot of riding in Afghanistan this won't really be a major concern.
That is not true. The military blankets the entire globe with limitations. The public doesn't get as accurate a reading as does the military on a daily basis. The whole system is a US military system in the first place, and they just allow others to use it. Which is why the EU wants Galileo up and running.
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Old 06-06-07, 08:26 AM   #11
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Can you calibrate the EDGE 305's altitude?
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Old 06-06-07, 10:24 AM   #12
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Quote:
Originally Posted by sogood
Actually, Garmin's GPS units also depend on barometric altimeter but gets real time comparison with its GPS data. GPS altimeter aren't as sensitive and can have large fluctuations when there are reception issues.
The Edge 305 does this. The cheaper Edge 205 uses the GPS elevation.
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Old 06-06-07, 10:25 AM   #13
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Quote:
Originally Posted by varian72
Can you calibrate the EDGE 305's altitude?
The Edge 305 calibrates itself through the GPS when you turn it on. This is a very convenient feature compared to most barometric altimeters that you have to manually calibrate every day.
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Old 06-06-07, 11:22 AM   #14
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Quote:
Originally Posted by KevinF
Vetta makes (or at least made) their V100A which could have both altimeter and cadence information.
I ride the V100A, and have been happy with it. Altitude readings seem to be pretty close to what I get if I map out a ride with my Topo software. The cadence allows you to pull up average cadence, which is helpful over some of the more common cadence computers.
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Old 06-06-07, 11:45 AM   #15
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Some altimeters show you only the current elevation or cumulative elevation gain. Others store data points along the route so that you can create elevation profiles for your rides. I think this is a useful feature, but you get what you pay for.

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Old 06-06-07, 07:36 PM   #16
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Trek has a speed/cadence/altitude/gradient computer, no idea how well it works though. At around $180 definitely not cheap.
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Old 06-06-07, 07:40 PM   #17
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Quote:
Originally Posted by lvleph
That is not true. The military blankets the entire globe with limitations. The public doesn't get as accurate a reading as does the military on a daily basis. The whole system is a US military system in the first place, and they just allow others to use it. Which is why the EU wants Galileo up and running.
Insert "Why do you hate American?" here.
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Old 06-06-07, 07:42 PM   #18
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Not to burst your bubble, but Galileo is pretty much dead, apparently getting everyone to work together on it has been even more troublesome than the A380.
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Old 06-10-07, 01:24 PM   #19
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I've used a Polar 720 HRM/cyclecomputer for 3 seasons now. Provides all the standard bike computer functions including cadence (wireless sensor) and gradient (derived in PC-based software from recorded data). Can record data at 5 second intervals and supports transfer to PC via USB dongle (additional purchase). Altitude recording is barometric, it is repeatable and good enough (we're not surveying for the US Geological Survey!) for my needs. HRM is coded (almost impervious to power line interference), wireless speed and cadence sensors are sometimes affected but I can edit out errors in software when I download the data to my PC. [BTW, Polar's PC software only runs on Windows, no Mac or Linux that I know of.]

Attached is an altitude and cadence plot from the 2006 Reston Century. I'm not sure why the cadence sensor dropped out for part of the ride - I probably bumped the sensor and didn't notice. Note that the start and end altitudes differ - this was caused by air pressure changes during the day.

I wouldn't rely on GPS-derived altitude data. Accuracy is not as good - it can be off 1.5x horizontal position data (or more), plus differences between the system's mathematical model of the earth's surface and reality. Unless you need or want the mapping functions, save your money and put it towards a computer that does what you need.
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File Type: jpg Restoncenturyaltitude2.jpg (11.0 KB, 24 views)
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Old 06-10-07, 05:44 PM   #20
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Quote:
Originally Posted by DrPete
Unless you plan on doing a lot of riding in Afghanistan this won't really be a major concern.
+1. Current civilian GPS is accurate within about 10 feet.
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Old 06-10-07, 05:48 PM   #21
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+1. Current civilian GPS is accurate within about 10 feet.
That's horizontal, not vertical, right?
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