Glacier - Greenland
Glaciers are slow moving rivers of ice. Tidewater glaciers, such as this, terminate in the sea, calving off icebergs. Drone survey techniques, using 3D photogrammetry, LIDAR or a combination of the two, can measure the speed of glacial advance, as well as quantify lost mass in high resolution. Though similar observations can be performed by satellite, the coverage in high latitudes may be patchy, and the resolution is poorer and prone to interference by a number of factors.