Online gpx editor3/17/2023 ![]() Then edit the configuration file ( ) - you should enter valid data for the folder for caching aerial photographs and maps and the file name of the image shown. Just download the files and unpack the archive into a folder. For maps and aerial photographs, a high speed internet connection is required. Another cause could be a willful distortion by the US armed forces who are the owner of the GPS, but "Selective Availability" is said to have been switched off. ![]() This could be caused by a clock issue of my Garmin Oregon, but I did not find any related information on the web. I discovered two cases where a later waypoint has an earlier timestamp than its predecessor - I published one of these cases in the Lounge ( Proof of Time Travel). Hence, we should think that the timestamps of our way points are perfect. The Global Positioning System actually relies on extremely exact time values. I added a setting for the minimum distance to a previous point for calculating the ascent / descent. Also in mountain regions, erratic values can be reported. When calculating total ascent/descent, these oscillations could sum up to several meters and severely distort the results for tracks in the plains. With the cold temperature of some -10C at that time, the elevation difference from my home to my brother's home stretched from 100m to 110 m = 100m * 288K / 263K.Īnother issue is that there are minor oscillations by typically less than one meter. The altimeter uses a conversion factor for air pressure to elevation, about 12 hectopascal per 100 m - that's valid for 15 C or 288 K (degrees Kelvin). After a lot of search through the web, I found the major reason: air temperature (see also "Grundlagen - Luft Luftdruck" link removed, original page is no more available and redirection points to spam). E.g., my brother's home's location was 10m higher than expected. I decided to switch the automatic calibration off, and then found systematic deviations from the expected values. The elevation plot can be totally useless. Since no information on that calibration is recorded, you cannot know when it happened and by how much the elevation values were changed from then on. They typically use the values from the barometric altimeter, but from time to time calibrate it with the satellite values. Modern GPS receivers also have a barometric altimeter. The determination of the elevation from the satellite is not good. I hope the automatically generated classes could thus become more intelligible and more useful.
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