Hi Ben, Please refer to the ContextCapture user manual page 244: "ContextCapture describes georeferenced positions using two geographic (longitude, latitude) or two projected (X, Y) coordinates, complemented with ellipsoidal height, which is the height above the reference ellipsoid (usually WGS84, but it may be a different ellipsoid, e.g. GRS80, for some spatial reference systems). Ellipsoid height differs from orthometric height, which is closer to the popular height above sea level. ContextCapture uses ellipsoidal height instead of orthometric height, because the former has a simple and unambiguous mathematical definition, whereas the latter is based on a geoid height grid subject to sampling and accuracy issues."
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