Add the option to pin tracks to the surface of the 3D terrain

[jimmyangel]

Currently, tracks are being visualized in 3D using the altitude information recorded by the GPS. Naturally, the data does not exactly match the altitude of the terrain model, resulting in tracks that look like they are floating over the terrain and/or sinking under it. Adding the pin option would draw the track exactly on top of the terrain model, which should provide a more “natural” view of the track.

[mhaberler]

for flights, it would be more helpful to have the 3D visualized track and (optionally) a projection of the track onto the ground (wherever the terrain model thinks ground is in terms of altitude) - not sure how this can be done with Cesium

assuming it is: a more general solution would be to have a track radiobutton options 'Add track over ground' and 'Pin to ground'

[jimmyangel]

It can be done in Cesium, but it is tricky to do with a 'path'