Elevation data explained

Position → Complete… → Elevation fills in missing elevation for a track or route (see Complete elevation data for the how-to). This article is about where that elevation actually comes from.

RouteConverter's OpenSource Edition works entirely from elevation models you download once and then use offline — no server round-trip, no key required.

NASA SRTM

The Shuttle Radar Topography Mission mapped almost the entire planet's elevation from orbit in 2000, using radar rather than satellite photography. It's the baseline elevation dataset most offline GPS tools build on, freely available worldwide with a resolution around 30 meters.

Jonathan de Ferranti's DEM

SRTM has gaps and rough edges, especially in mountainous or high-latitude terrain that radar handles poorly. Jonathan de Ferranti's Digital Elevation Data fills those gaps by hand, merging SRTM with other sources and manual corrections for areas where the raw satellite data falls short — useful anywhere your track goes somewhere SRTM alone gets wrong.

Sonny's LiDAR DTMs

Sonny's LiDAR Digital Terrain Models of Europe go further still for European countries with public LiDAR survey data: resolutions down to 0.5–3 meters, an order of magnitude finer than SRTM. If your routes stay in Europe, this is as precise as offline elevation gets.

GeoNames and Google Maps

If you don't have local elevation tiles installed for an area, RouteConverter can look up elevation online instead: first via GeoNames, then — Google Edition only, as a last resort — via the Google Maps Elevation API. Both need a network connection at the time you run the action; neither is as precise as a good local DEM for rugged terrain.

Which to use

RouteConverter tries them in order — local tiles first, then GeoNames, then Google — and uses whichever answers first. Installing local .hgt tiles (SRTM, Ferranti, or Sonny's, depending on where you are) is worth it if you route in the same regions repeatedly: it's faster, works offline, and is generally more accurate for anything but flat terrain.