Find "Missing" Elevations with GPS VisualizerThe 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 databaseGPS 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 APIThe 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. The drawback is that there is a limit on the number of queries that can be performed in a day by each user, so GPS Visualizer cannot ask Google for all of your points. To get around this, GPS Visualizer contains a JavaScript-based Elevation Lookup Utility that has your browser perform the queries. To use this tool, your data must be in simple tabular format (easily accomplished using GPSV's plain-text converter); you must remove any existing elevation data; and you must have your own Google Maps API Key. Further instructions are on the Elevation Lookup Utility page. Quick single-point DEM database lookup:Coordinates (lat,lon): FIND ELEVATION →
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