Confused by the elevation value in your Propeller site? This article explains exactly what this number means (orthometric height), how it’s calculated using a geoid model, and how it differs from the raw GPS altitude (ellipsoidal height) from your drone.
Geotags only with takeoff elevation
If your drone is set up to record the height above its takeoff point in geotags, the dataset will usually show an elevation on the ground, mostly just above or below zero. Even if you're flying at the highest point on your site, the number you'll see will be around zero.
Geotags with GPS elevation
If your drone is recording the GPS elevation above "mean sea level," the data will be roughly aligned with the height of terrain in this area above the WGS84 ellipsoid used by GPS. However, GPS elevation data is accurate within only 20m, and there may be significant differences from a measured ground point. The WGS84 ellipsoid is also very different from the actual sea levels in many places by over 50m.
Ground Control Points or AeroPoints
If you use ground control points to make your data more accurate, you'll see an elevation based on the height datum used for the ground control. Most surveying data uses a geoid height datum—a correction that accounts for the planet's lumpiness and gives you an elevation much closer to what the sea level would be at a given location.
You can use the CRS setting in the Settings menu to choose a different coordinate system. Different ellipsoids or datums can affect the height displayed.
You can also use the settings in the top right to switch between metric and imperial units.
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