I have a shapefile with points in Adindan UTM 37N coordinates. Now there seem to be roughly two ways of converting those coordinates to WGS84.
When loaded in Google Earth Pro the points are about 150m shifted to the southwest compared to in QGIS.
In ArcGIS both of these behaviours are possible. When using on-the-fly projection with 'Adindan_To_WGS_1984_1' selected in the Data Frame Coordinate System Transformation the result is the same as in QGIS, (both using towgs84 geocentric translation -166,-15,204).
<None> is selected however the result is the same as in Google Earth. (This is only possible in on-the-fly projection, the Project tool always selects the closest match by default, just as with KML export.)
This Google Earth/ArcGIS
<None> behaviour is a black box for me, but in this case of converting Garmin GPX data in Adindan it seems to be the correct behaviour, so my question is: What happens in this case, and is it possible to do the same transformation with QGIS/proj4?
(I tried using +towgs84=0,0,0,0,0,0,0 but that causes an even bigger shift in a different direction)
For example: The Adindan coordinate [391000, 1221000] is converted to [38.002975, 11.045626] by QGIS and to [38.002148, 11.044758] by Google Earth.
Another way to use the coordinates is to interpret them as being WGS84 UTM 37N, then they transform to [38.002132, 11.043761]