Find "Missing" Elevations with GPS Visualizer
The problem: Sometimes you have geographic data that consists only of latitudes and longitudes, but you want to know the altitudes as well — because, for example, you want to colorize points by height above sea level, or draw a profile of a track. Here are some common reasons why you might have "flat" or incomplete data:
Solution #1: DEM database
GPS Visualizer's map, profile, and conversion programs now have the ability to instantly add elevation data — from a DEM (digital elevation model) database — to any type of GPS file. If you just want to draw a profile, or convert a single data file to plain text or GPX while adding elevation, you can use the simple form right here:
Or, look in GPS Visualizer's various input forms for the menu called "Add DEM elevation data," and choose one of the elevation databases (described in the table below). Complete copies of the SRTM3 and USGS NED databases, as well as a large number of SRTM1 and ASTER tiles, are stored on GPS Visualizer's server — that's more than 250GB of raw data.
Note that the elevation-adding feature will erase any existing altitude data (for example, from a GPS) that might already be in your file. Often, this is desirable; profiles made with DEM data are usually "smoother" looking than GPS, and typically contain fewer gaps or suspicious readings. (Speaking of gaps, there are a few in NASA's SRTM data, and that's unavoidable. If GPS Visualizer runs into one of these, it will not overwrite those elevations in your input data.)
DEM data sources
Solution #2: Google Maps API
The Google Maps API is able to return elevations for points anywhere in the world; these are usually (but not always) the same elevations you'd see in Google Earth. Google's data comes from a variety of sources and is sometimes (but not always) more accurate than the SRTM databases.
Quick single-point DEM database lookup:Coordinates (lat,lon): FIND ELEVATION →