Hi!
I’m new in here, excuse me if this sounds silly. All your maps are created by gps data, right? So where is all the altitude data, don’t you keep it and store it somewhere? Even in raw data it would be very useful for the cyclist community in my city. We could process it and search for the easiest routes through the hilly areas of the city
Elevation data (if you are talking about contours lines as seen on opencyclemap and others) is not recorded from gps survey but from :
http://wiki.openstreetmap.org/wiki/SRTM
Most of the maps are manually drawn based on GPS information from gps data, not automatically converted from the tracks. Because the maps are drawn in 2D, the OSM map database contains (almost) no altitude information. All current applications that combine OSM with altitude information take the latter from external sources; sly has already linked to one of these sources.
The raw altitude information from the GPX tracks is still available if you download these tracks directly*. You would probably need to put quite a lot of effort into extracting useful height maps from these - afaik, no one has managed to aggregate these tracks into a meaningful result so far. One of the problems seems to be that altitude information from consumer GPS devices isn’t really reliable, especially if the person creating the track didn’t pay attention to altitude information in the first place.
- I don’t know whether this information is also included when you download all GPS information for an area, rather than individual tracks. But it is stored on the server, so there should be a way to access it.
Thank you for responding guys
The SRTM data are not good if you want to extract the street altitude, the resolution is not high enough (not even the 1’ x 1’) and they should show mostly the altitude of the top of the buildings
I have tried to extract the data from http://www.openstreetmap.org/export/ (ticked the OpenStreetMap XML Data) but the altitude data are not included
So I’m left with the data from http://www.openstreetmap.org/traces (silly that I hadn’t noticed earlier 
). But still I have no idea how to isolate the data from my city (that’s Athens, Greece btw). Do you know of a way to do that? I understand that it’s going to be tough to make something out of them because of the technical difficulties but if it’s possible I’d like to give it a shot. The data from a small window like N 37deg 55’ 40’’ until 56’ 40’’ and E 23deg 42’ 20’’ until 43’ 20’’ or just a fraction of that would do it for a start
Another idea that I had is to gather all the data that my neighboring users have uploaded but I don’t know how to do that either
GPS altitude data can be horribly wrong or reasonably good but depends on many variables so it was decided quite early on in the project that such data wouldn’t be used. It’s available in the uploaded GPS traces I think but your mileage may vary!