GPX differences between apps
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Boggy B
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Re: GPX differences between apps
I'd say GPS accuracy is the main issue here. But yeah, in a perfect world where you can record an infinite number of 100% accurate waypoints, the maximum distance/vert you can achieve is dictated by how small of steps you take!
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skyrme17
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Re: GPX differences between apps
It's not solely GPS accuracy. The core problem is how to measure more accurately a sum when each step has a given error. More measurements add more noise, while fewer measurements miss actual information. One point correctly made is that tying elevation to an actual contour-elevation map greatly reduces elevation error.
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Boggy B
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Re: GPX differences between apps
Right, if your tracking device is computing vert stats off a barometric altimeter then localized variance in weather/conditions will screw it up.
Or if it's using GPS altitude then GPS drift will screw it up.
But elevation lookups are also highly susceptible to GPS drift:
So you're walking along a narrow ridge or cliff, your device's GPS skew is a couple feet off the side tracking terrain hundreds of feet below, then you walk down the other side and now based on elevation lookups you've gained hundreds of extra feet regardless of your breadcrumb frequency or later horz/vert resampling. Both your GPS altitude and baro could be more accurate than lookups in this scenario, which is relevant to half of the 14ers.
Probably the best we can do is compute stats from the average of all public GPX for a given route, using DEMs for vert. Or manually post-process your tracks. Or just use net gain (to summit) for vert, there are some diehard net gainers lurking here.
Or if it's using GPS altitude then GPS drift will screw it up.
But elevation lookups are also highly susceptible to GPS drift:
So you're walking along a narrow ridge or cliff, your device's GPS skew is a couple feet off the side tracking terrain hundreds of feet below, then you walk down the other side and now based on elevation lookups you've gained hundreds of extra feet regardless of your breadcrumb frequency or later horz/vert resampling. Both your GPS altitude and baro could be more accurate than lookups in this scenario, which is relevant to half of the 14ers.
Probably the best we can do is compute stats from the average of all public GPX for a given route, using DEMs for vert. Or manually post-process your tracks. Or just use net gain (to summit) for vert, there are some diehard net gainers lurking here.