3.2.2. Aerial imagery

Photos taken from the air, usually from an aircraft, are referred to as aerial imagery or photographs (Fig. 5). These images provide valuable information about landscape changes by comparing photos over time. When aerial images are georeferenced, i.e. located with respect to a geographic or projected coordinate system, they can be used as raster layers in GIS (Burrough and McDonnell, 1998). The different types of aerial images include black and white, true colour, panchromatic, and infrared and can each be used for different purposes (Campbell, 2002). 

Fig. 5. A sample orthophoto, with a resolution of 50 cm, showing the study area of Fribourg, Switzerland. This photo comes from Swisstopo (2013) and must only be used for visualization purposes in this paper. Reproduced with permission of Swisstopo (BA13016).