Monoscopic observation easily causes perspective reversal and may lead to 
non-systematic texture description. This has been many times during interpreta- 
i tion of Landsat imagery, showing the importance of the adaption of texture- 
le names and classes to the Gestalt-properties of the visual perception. 
3. It is also important to remind that the Gestalt-effects makes 
it difficult to make thematic maps by visual interpretation. Photomorphic 
units, as the result of gradual image differentiation, have to be considered 
as holistic land units. 
ren- 
H H . 
lt A METHOD FOR A "NATURAL" VISUAL IMAGE INTERPRETATION 
zed 
Based upon the Gestalt-theory and the observations made, a 
.nct method for visual image interpretation has been elaborated. Although it had 
e been used already succesfully (M.EL HAG 1980), it still remains a preliminar 
st version. The principles and the general procedure for each image analysed, 
lage- are following 
(1) be aware of the capabilities for Gestalt-perception. Especially, trust 
upon the ability of image completion and the differentiation of similar 
he patterns. Adjust the size of the image to the field of visw : if necessary 
d. enlarge or reduce the scale so that each entity you would like to analyze can 
the be seen at once (use photographic enlargements, projections or make mozaics). 
een : 
is) (2) Start using the image as the unique source of information. In the first 
stage no relations with the ground truth need to be made. 
(3) Follow the gradual differentiation process. Mark on a base map the features 
which will be percieved first. If you can recognize them, describe with 
terrain-attributes. Otherwise, describe using photo-attributes. 
(4) Check what Gestalt-laws have been acting upon the differentiation. This 
will help you to restructurize. Compare differentiated parts with the 
whole, with ground-truth. Try to describe as much as possible in terms of 
terrain attributes. In the beginning this will not be systematic nor comple- 
te. 
(5) Check the boundaries you have drawn. Compare with the Gestalt-laws and the 
ground truth. Adjust boundaries and descriptions when you can not accept 
them. Once accepted, the limits of the photomorphic units will not be 
changed anymore. Additional information will only be descriptive and will 
not differentiate map units further. 
(6) Continue the image classification with several of these differentiation- 
restructurization or analysis-interpretation loops (steps 4-5). Map each 
time more smaller photomorphic units within the larger ones and add more 
description into a symbolic code or table. Stop when you judge a sufficient 
level of detail is reached. 
(7) Restructurize in a table the descriptive image codes according to the 
ree 
hierarchy of differentiation (macro-micro-units) and to the attributes whic 
S have been used for differentiation (tracing the boundaries) and description. 
1 
When different image-types are available, they should be analysed 
one after the other using following procedure 
(a) Start with small-scale satellite imagery : use the spectral band or image 
je- composite which is the most complex image (high contrast and much detail). 
901 
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