[closed] Elevation data with Memory Map gpx files

[pinkyperk]

I know there are plans to have elevation data available in AQ, but I thought I would share an interim way of adding DEM (Digital Elevation Model) data to an existing gpx file, which I have found quite useful and which works successfully in AQ. This involves using online website http://www.gpsvisualizer.com/elevation. Just load up the GPX file then it is easy to add the data and save the file again, complete with all the data included. The only slight problem I encountered is that when starting with a route file it converts it to a track file and sometimes it is difficult to use the Dynamic Profile in AQ with this file. Just one query - the elevation data in AQ is showing some variation from the actual embedded elevation data in the gpx file. E.g. I have a waypoint Hollins Clough which is 473 m altitude (as defined in the gpx file from loading DEM data). In AQ it shows it as 425 m. In the detail it shows 425 m(incl- 49). I wonder if you could explain this? All of the elevations seem to be similarly different in AQ from the actual elevation in the gpx file. Many thanks for your help.

[Psyberia-Support]

Hi again and sorry for the delay.

First, you'll have the ability to convert routes to tracks in the next version (by exporting the route in CSV format and importing the created file as a track).

Concerning the elevation differences, this is a bit technical so I hope I'll be clear enough (but let me know if I'm not):
There are different "kinds" of altitudes, most importantly:
- The "geoid altitude" (aka the "natural" altitude), which is the elevation of a point from the sea level (more precisely a deformed sphere called the "geoid" or EGM96, made to match the sea level worldwide as much as possible) to any point;
- The GPS altitude, also called WGS84 altitude, which doesn't use the geoid as referential, but a more simple sphere (to have easier computations). Depending on where you are on the Earth, the difference can be important (up to 100 meters), as shown here: http://en.wikipedia.org/wiki/Geoid#medi ... ragebw.png.

The GPS and the GPX files deal with WGS84 altitudes, whereas the application converts all altitudes to the "natural" geoid altitudes (used in topo maps for example), and this is why you see differences between your GPX file and the application. In your particular case, -49 meters.

Here is the same explanation in the online help: http://www.alpinequest.net/en/help/1.4/ ... management