Fig.1 Location map 
INTRODUCTION 
The purpose of this investigation is the evaluation of the potential of ERTS-1 
imagery for soil survey. The imagery has been related to the results of a survey 
training and research project, which the ITC Soil Dept, in collaboration with 
Spanish governmental and scientific authorities, has carried out in the Merida 
region is S.W. Spain over the past 6 years. 
The investigation was made possible by NASA which approved the ITC Principle 
Investigators proposal and supplied the imagery. Fieldwork was conducted through 
the generous co-operation of the Spanish authorities which permitted groundtruth 
surveys in May, June, and October 1973. The fieldwork was planned to coincide 
with several of the days on which imagery for this study was scheduled, but un 
fortunately did not coincide with the time (March 1973) at which the imagery was 
actually completed. Recently, however, imagery of the months of September and 
November 1973 became available. 
2 
The area of investigation is approximately 25, 000 km and lies in S.W. Spain, 
close to the borders of Portugal, between geographical longitudes 5°E and 7°E 
and lattitudes 38°N and 40°N (see fig. 1). For part of this area (fig. 2),approx- 
2 
imately 1200 km , staff and students at ITC have carried out a soil survey training 
and research programme using aerial photographs. For the remaining part of the 
area the information consists of a series of maps issued by Spanish authorities in 
different scales from 1 : 250, 000 up to 1 : 1, 000, 000.