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sses of Table I and a second one with the seven grouped classes of Table II. 
They have been compared with the conventional maps mentioned above. The digi- 
tal map with seven classes significantly improves the conventional map at 
scale 1:1,000,000 . The digital map with fourteen classes improves the conven 
tional map at scale 1:400,000 and the comparison with the 1:200,000 shows so- 
me improvements and some deficiencies in specific units. 
As a result of the whole process we have followed some general conclu- 
sions can be drawn. 
1) The spectral classes with high reflectance values indicate the occu- 
rrence of calcic xerochrepts, typic xerochrepts or typie haploxeralfs soils 
developed upon sandy sediments, grypsiferous marl or limestone, corresponding 
to the physiographic unit of low hills. 
2) The spectral classes with medium reflectance values indicate the occu- 
rrence of typic haploxeralfs or lithic rhodoxeralfs as dominant soil, corres- 
ponding to the physiographic unit of limestone plane. 
3) The spectral classes with low reflectance values indicate the occurren- 
ce of typic xerorthents or calcic xerorthents soils, corresponding to the phy- 
siographic unit of scarpments. 
4) The vegetation which is very easily detectable by digital analysis has 
been very helpful as an indirect means to differentiate soils and physiogra- 
phies. 
In conclusion, digital analysis of LANDSAT MSS data aided with aerial 
photo-interpretation has been succesfully used to produce physiographic soil 
maps of a region of 2,250 Km? in central Spain. 
Madrid, June 1978