Barometric altimeter vs mapping verts

[9606]

Why is there so much discepancy between the vertical feet reported by:
Garmins
Polar units
mapmyride
DeLorme
etc.,

What is the most accurate mapping website? Has someone done a comprehensive comparison?

How sensitive are the barometric altimeters found in some cyclometers to normal changes in weather. Say, just during a 12 hour bicycle excursion.

It is 2010. Is it unreasonable to expect more agreement amongst all these data sources? I am tired of doing a ride and having various vert reports be as much as 20% different.

 

[sitzmark]

Agreed - vast differences.

What's correct??? Not sure, but I do throw my Garmin Edge 305 in my pocket when I ski and it very closely records the published elevations of peaks and base lodges (usually within 50ft or so). Occasionally it will throw out an outlier or two for speed that I know can't be correct, but in general the speed tracking is reasonable too. I've put the 305 on my dash and driven with it to verify against car speedo and it matches closely - some delays under tree cover, etc.

I tend to go with what the garmin spits out, but wouldn't bet any money on it.

 

[alienator]

Why is there so much discepancy between the vertical feet reported by:
Garmins
Polar units
mapmyride
DeLorme
etc.,

What is the most accurate mapping website? Has someone done a comprehensive comparison?

How sensitive are the barometric altimeters found in some cyclometers to normal changes in weather. Say, just during a 12 hour bicycle excursion.

It is 2010. Is it unreasonable to expect more agreement amongst all these data sources? I am tired of doing a ride and having various vert reports be as much as 20% different.

Why:

• GPS elevation measurement isn't terribly accurate
• Barometric altitude measurement should be more accurate (with proper calibration) but can by influenced by weather changes
• Mapping sites do not record elevation changes accurately at all
• Different software and different firmware can smooth altitude measurements differently