Aerial photo interpretation

The aim with aerial photo interpretation within NILS is to:

• Provide information about the composition of the landscape
• Follow changes in the landscape
• Create a base for field inventory oriented towards specific elements
• Provide information for estimates of conditions in areas that are not visited in the field
• Create a basis for field maps
• Together with field data act as a base for two-phase estimations
  

The aerial photos used are infrared photographs (IR photos) taken from a height of 4 600 meters which gives a scale of about 1:30 000.

NILS has chosen to use IR color photos since they are superior to other types of film when it comes to interpreting types of vegetation. The difference in reflection between different kinds of plants is greatest within the infrared wavelength area, which leads to good possibilities of distinguishing between different types of vegetation. These reflection differences are due to several factors, e.g. the surface of the leaves and the water content in the ground and the vegetation.

The aerial photographing is done with digital aerial cameras, and interpretations are done in digital aerial photo interpretation stations. With a polarized screen and special glasses a three dimensional picture will emerge with the help of two aerial photos in a so called stereo model.

The design of the method for aerial photo interpretation has been made in close cooperation with the Department of Physical Geography and Quaternary Geology at the University of Stockholm.

More information about aerial photo interpretation in NILS is available in the manual Instruction of Aerial Photo Interpretation in the National Inventory of Landscapes in Sweden.