The concept of remote sensing concerns observations from satellites, aeroplanes, drones etc. The measurements may be performed by means of regular pictures, laser, radar or e.g. infra-red radiation.
The satellites fly in fixed orbits. As the satellites fly over the same areas repeatedly, they can be used for continuous monitoring and measuring of changes, e.g. the geographical distribution of glacier in Greenland. Asiaq uses satellite measuring to map large open land areas.
Pictures from low-flying aeroplanes are more accurate and detailed than satellite photos. On the other hand, many pictures are required as you can only see a small section of the earth in a single picture. Asiaq uses aeroplanes for detailed surveying of towns and for open land mapping. In the open land, you will thus see coastline, lakes, rivers, glacier and nunatak.
A series of regular aerial photographs cannot be used for measuring distances as the distance scales vary due to the differences of height in the terrain, the inclination of the camera in the plane, etc. In order to obtain the same dimensions throughout the photo series (the total picture of an area), all image data from an area will be converted into an ortophoto. An ortophoto has the same dimensions all over the photo and thus has a fixed distance scale just like a conventional map. Ortophotos contain a lot of information about the terrain and may be used in combination with the digital maps in a GIS tool.