A group of us rode 100km on Friday. Me, with my Garmin 301, recorded 4000 feet of climbing. Another in the group with his Polar recorded only 3000 feet.
What is everybody’s experience with measuring cummulative climbing? What devices are you using?
Trust GPS
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Trust GPS
Actually trust neither… The Polar uses a rudimentary barometric gage which must be constantly recalibrated, and even then leaves much to be desired. If you are using a Garmin such as a FR201 or an FR301. It also is not the gold standard to measure altitude by. The GPS is great for position but does not do well with triangulating vertical measurements.
If you want a corrected measurement, upload the data from the Garmin to Motionbased or a topographic mapping program and you will get the actual readings that are extrapolated from a topographical data base.
I have and use both an FR301 and a Polar S720i, so I actually speak from experience.
Aero is on the money. I have a 720 and a 201 and have used both simultaneously on a number of occaisons.
You must understand the limitations of the technology to make a call on this and by analysing the graphs of recording over time you can see where the problems lie.
The GPS is noisy, and is jumps around quite a lot, making it useless for small (20’ say) differences. Whilst this averages out over time (or should) there are often some big spurious spikes that completely ruin the ongoing tally (and hence the total ascent). However the readings are absolute so you do not have to set anything.
The Polar on the other hand, is very smooth and good for smaller changes. It is a little sluggish, but gives you good change in 10’ or less. The problem with the Pollar is that is not absolute it is relative, so you must set a known elevation in it first or else the absolute (ie the altitude) is meaningless. The ascent is relative so that is OK. The other big problem is the change over time of barometric pressure. This has a big affect over some time (say 1/2IM or IM distance) and can be quite a severe change - dwarfing the actual rises and falls of the course.
My advice
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the polar is more accurate for ascent, but be careful if you are using for long events or there is a mjor weather change.
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GPS is more accurate for instant altitude readings.
In any case download the data and you will instantly see (noise or creeping changes) if the information is useable.
I did get my altitude from uploading to MotionBased - I use a Garmin 301. So you think MB is overlaying the data on a topo map? Hmm, maybe I’ll e-mail them…I’ll report back here.