[Talk-us] OSM Elevation Data

[Mike N]

On 10/6/2022 6:47 AM, Greg Troxel wrote:
> OSM currently
> only has elevation tags on a few point objects, like peaks.  Routers use
> separate databases of elevation, where they can look up elevation from a
> dataset not stored in OSM.  There are lots of examples, and the first
> that comes to mind is OsmAnd which shows elevation profiles on routes
> when the roads and their nodes do not have elevation

   There are at least 2 problem use cases with an an external elevation 
data set which is acquired from above such as from a plane or space shuttle.

  1. Roads through tunnels are assigned the elevation profile of the 
mountain above.   However in practice 99% of tunnels have a constant 
slope from one end to the other and a router could connect them with a 
straight line elevation between the 2 entrances.

  2. Roads within canyons can have elevation errors - the road can be 
intermittently hidden behind the canyon wall due to the viewpoint of the 
measuring device.   The automatic profile as calculated has wild swings 
in elevation every time the road enters or leaves view.

   #2  has no automatic solution.   One possibility would be to assign 
elevation to those sections of roads in OSM that are likely to have this 
type of error.   Are there other ways around creating OSM elevation 
tag(s) and the can of worms that would open?