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EXTRACTION OF TEXTURAL SIGNATURES FROM 
FOREST AERIAL PHOTOGRAPHS USING A SPECIAL-PURPOSE 
DIGITAL COMPUTER 
W. Schneider 
Institut für Vermessungswesen und Fernerkundung 
Universität für Bodenkultur 
Peter Jordan Straße 82, A-1190 Wien, Austria 
Abstract 
The reliable discrimination and identification of forest stands from 
aerial photographs by automatic methods requires a classification 
process based on both textural and spectral parameters. These 
parameters, besides from being relevant for the classification process, 
should satisfy certain requirements: a) The extraction of the para- 
meters from photographs should be possible at a reasonable 
b) The parameters should show little variation with 
expenditure. 
or they should at least be related to the angle 
the angle of view, 
of view in a simple manner. 
In this contribution, a method for the extraction of textural signatures 
satisfying the above-mentioned requirements is investigated. The 
method is based on the use of the Quantimet 720 image analyzer. 
With the aid of this small special-purpose digital computer, the input 
image is decomposed into a series of binary images by hardclipping 
at varying hardclipping thresholds. In these binary images, number, 
area and perimeter of isolated objects are determined. These para- 
seen as a function of the hardclipping threshold, represent 
meters, 
se relationship to properties of the 
textural signatures showing a clo 
individual tree. 
The usefulness of these textural signatures for automatic tree species 
recognition from aerial photographs is discussed on the basis of 
experimental data.