Altitude difference between Polar and Strava

[RABUBI]

Picked up something interesting yesterday

 

 

Did a 60odd km ride yesterday

 

Use a Polar RCX3 that uses basically google maps to calculate elevation gain.

 

Total ascent 790m

 

Also used my Samsung to record the ride on Strava and total elevation gain is 928m

 

 

I thought that both uses google maps as a based to calculate elevation gain

 

Just funny that there is such a big gap

 

Any thoughts?

[JanJan]

Im just quoting a guy from the webz:

 

"There are three ways (relevant, anyway) to get elevation data:

1) barometric pressure. Quite accurate if you have it, and calibrate it. Most folks turn on their computer and ride, which doesn't help that.

2) GPS. Crapton awful for elevation, for a variety of reasons, but essentially, a low-power receiver can't pick up a good enough constellation of satellites for the trigonometry to work out very well - especially from ground level.

3) read the GPS location data, then using topographic data, extrapolate and figure it out. Can either be decent or awful - for example, if you ride across a canyon bridge, this will assume you got your tires wet at the bottom - hella climb, though, buddy!

Strava uses 3. A higher-model Garmin uses 1, if you are patient enough to let it. Some websites (GC, mapmyride) will combine 1 and 3 and do some fuzzy math to try to get it as right as they can figger. Some toys use 2 to display random numbers while riding.

In other words, it's like the old saying. "A man with one watch knows what time it is, a man with two is never sure." Consider them all for crap - just pick one that suits you and go with it.

As long as it isn't Strava."

 

Have you noticed that when you finish a ride, Strava updates your distance and elevation after 5 minutes? It is a built in program to cross reference your route to the nearest available elevation maps (I don't think it is Google maps) and nearest available weather conditions.

 

But I am pretty sure ALL GPS tracking devices overshoot. The most accurate way of determing altitude is with a dumping level, because there aren't any engineers who build road-gradients using GPS values.