Store altitude information in maps

[berndth@…]

Currently, maps created with JOSM contain longitude and latitude information. GPS receivers usually also measure an altitude coordinate. Since altitude information is interesting for many applications, I request that this information is not thrown away, but stored in the maps. This would not require any additional effort during map tagging, but would result in a more complete map basically for free (once implemented in the editor, of course).

One way this could be done is by using the altitude information of the nearest GPS measurement for a respective node, if a GPS measurement is "close enough" (with an upper bound of maybe 100m, might be configurable). I am well aware that this value might jump at bridges, and might not be very accurate, but it is better than loosing this information completely. Just think of planning a bike trip in the mountains.

I am putting the priority of this enhancement request to "critical" as information is lost on every tagging done without altitude saving.

[Gabriel Ebner <ge@…>]

There are good reasons why we don't store altitude information on every node:

• It's massive bloat. 63M extra tags.
• It's inaccurate as hell. GPS receivers have way better 2D accuracy and still you have to average a few tracks to get usable data. Just adding unprocessed altitude from the tracks isn't going to work.
• It works just for linear features. You won't have any data for the hill on the side of the road.
• You can already get pretty good DEM data from SRTM.

I don't see any reason to add this to JOSM unless adding it becomes commonplace. If you want it nonetheless, you can implement it as a plugin.