SRTM
The elevation data download looks to be very inaccurate
2016-06-25 15:56 Stored in:Conceptual
Problem: When TrailRunner mini downloads elevation data from the internet service, the elevation data looks inaccurate and does not match the GPS or odometer recordings of my GPS device. Or TrailRunner mini seems to remove elevation data from files I have imported.
Description: TrailRunner mini downloads elevation data from a source that is based on the data provided by the NASA's Shuttle Radar Topography Mission (SRTM), which is a satellite scan of the earth surface. The resolution of the scan is about 30 meters (98 feet) in the more popular areas of the word and 90 meters elsewhere.
What could happen now is that when your GPS device made a location recording that is not very accurate, the position may hit a spot where the actual altitude differs by a large amount to what the real position would describe. For example the false position recording may not describe the path you're on but the neighboring tree top, house roof or cliff top.
This may lead to crazy point to point slopes of 30% and more. So TrailRunner mini filters out such implausible elevation data as good as it can. Otherwise all the cumulative ascend and descent data would be far of plausible values. This filter also takes place for imported files that need no elevation data download but also contain crazy point to point slopes.
Please understand that the root cause to all this is the false GPS point recording in combination with a possible lack of resolution of SRTM data. TrailRunner mini can't guess what's right, but can easily remove what is obviously wrong.
Description: TrailRunner mini downloads elevation data from a source that is based on the data provided by the NASA's Shuttle Radar Topography Mission (SRTM), which is a satellite scan of the earth surface. The resolution of the scan is about 30 meters (98 feet) in the more popular areas of the word and 90 meters elsewhere.
What could happen now is that when your GPS device made a location recording that is not very accurate, the position may hit a spot where the actual altitude differs by a large amount to what the real position would describe. For example the false position recording may not describe the path you're on but the neighboring tree top, house roof or cliff top.
This may lead to crazy point to point slopes of 30% and more. So TrailRunner mini filters out such implausible elevation data as good as it can. Otherwise all the cumulative ascend and descent data would be far of plausible values. This filter also takes place for imported files that need no elevation data download but also contain crazy point to point slopes.
Please understand that the root cause to all this is the false GPS point recording in combination with a possible lack of resolution of SRTM data. TrailRunner mini can't guess what's right, but can easily remove what is obviously wrong.