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PRELIMINARY RESULTS OF THE INTERPRETATION 
OF ERTS-1 IMAGERY FOR A SOIL SURVEY 
OF THE MERIDA REGION, SPAIN 
F.W. Hilwig**, D. Goosen*, § D. Katsieris*** 
ABSTRACT 
The purpose of this investigation is the evaluation of the potential of 
ERTS-1 imagery provided by NASA for soil survey. The imagery has been 
related to the results of an aerial survey training and research project, 
which the ITC Soil Department, in collaboration with Spanish governmental 
and scientific authorities, has carried out in the Merida region in SW 
Spain over the past 6 years. 
The investigation was made possible by NASA which approved the ITC P.I. 
proposal and supplied the imagery. Fieldwork was conducted through the 
generous co-operation of the Spanish authorities which permitted ground 
truth surveys in May, June, and October 1973. These unfortunately could 
not be completed at the same time as the imagery in March. 
Both black and white and colour imagery have been studied using various 
bands and a number of filter and illumination combinations at scales Vary- 
2 , 
ing from 1 : 100,000 to 1 : 1,000,000 using an I S Addcol Viewer and other 
photograhic means. Other experiments with respect to contrast and regi 
stration of the original images and converted products were carried out in 
the ITC Department of Photography. 
Preliminary results seem promising. Major landforms and some sub-divisions 
could be easily recognized. Water bodies, river courses, extensive areas 
of miocene clays and more recent coarse textured deposits could be delineated 
and existing soil maps at scales up to 1 : 100,000 could be updated. It should 
be stressed that the investigation was completed in a well mapped area; the 
same favourable results might not have been obtained in an unknown area. 
^Professor, ** Senior Lecturer, and *** M.Sc. Student in Dept, of Soil Surveys