A while ago Gaia updated their altitude algorithms so that ascent/descent, low and high were consistent on the web and the device. At the time the blog post (https://blog.gaiagps.com/improved-statistics-in-gaia-gps-for-ios-android-and-gaiagps-com/) acknowledged the controversy when calculating altitude but felt they had a really good solution. They also said they were open to further discussion but I did not see any subsequent discussion.
I'm conflicted how to approach the problem. I compared with Google Earth's elevation profile and get very different answers and to me GE's statistics are much more accurate, however Gaia's support is pretty confident in their results.
My analysis suggests Gaia over smooths the data which under reports ascent especially in the case of rolling hills. The conflict is that over smoothing doesn't affect the results if the elevation over is track is monotonic (up, down or flat) so Gaia will produce very good results for those cases.
If they use a sliding window average-er for smoothing and the window is too wide then it will significantly under report rolling hills. I think if they did something like a low pass filter (such as a Fourier transform and remove the high frequency components) I think it might work better.
But I am happy that they still export the raw measurements in the GPX and KML they export so that I can do my own analysis. I certainly don't want that to change.
I wonder whether a) different GPSs have different characteristics and b) different areas have different distortion.
This makes me think it might be nice if there were a suite of elevation calculation algorithms or if we were able to parameter-ize the algorithms, such as changing the size of the averaging window.
I'm curious what people think.
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