Aspects of the ITC approach to vegetation survey

The paper deals with aspects of vegetation survey with the use of aerial photo-interpretation, especially the methodology developed during the last decade at the International Institute for Aerial Survey and Earth Sciences (I.T.C.), Enschede, The Netherlands.
The purpose of vegetation survey and aspects of the mapping scale are indicated, followed by a discussion on the different types of remote sensing imagery and their applicability in vegetation surveys. Three alternative (in vegetation survey often used complementary) approaches of applying photo­interpretation are given : the landscape-guided approach, the photo-guided field survey and the photo-key method. The authors argue that the landscape­guided approach, characterized by a systematic photo-interpretation of the entire survey area as a basis for stratified fieldsampling is the best approach for vegetation survey, in particular for semi-detailed and recon­naissance scales.
Field sampling strategies are indicated and the use of photo-interpre­tation on the one hand as an indispensable tool for objective stratified sampling, on the other to delineate boundaries, is emphasized. For the classification of the field samples the use of sociological (ecological) species groups as floristic characteristics of vegetation types (communities), which serve in their turn as a base for the map legend, is recommended.
Finally the presentation of the legend units (in an illustrative for­mat, placed in a two or three dimensional axes system in which the axes have a clear ecological significance) as developed in the I.T.C.-methodology is described and illustrated.