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).