203 
ds. 
3. 3 Comparison of ERTS-1 imagery interpretation with existing maps 
A series of two interpretation maps based on one season (March 1973) ERTS-1 
imagery for soil survey purposes are presented on two different scales. Both 
l 14‘ 
maps were drawn on colour composite paper prints prepared by the Photographic 
Department of ITC. The composites were made using bands 4, 5, and 6 with cor 
responding blue, green, and red filters. In this way a simulated false colour ap 
pearance was achieved. The composite was made of bulk material received from 
NASA before correction of the original negatives. As a consequence the influence 
of band 4 was limited due to low contrast. 
:der with 
3.3. 1 ERTS-1 Interpretation map and soil map of Spain, scale 1 : 1, 000, 000 
re. 
The ERTS-1 map, scale 1 : 1, 000, 000 (fig. 2) was interpreted using available 
sources of literature and a limited amount of field check (3 weeks). Table 1 con 
tains the summarized results of the fieldwork regarding physiography, natural 
vegetation/land use, and soils; 10 mapping units have been distinguished. The 
soils have been described in simple terms of colour, texture, soil depth, and 
profile development. 
* 
Comparison with the S. W. part of the Soil Map of Spain of the same area (fig. 3) 
is difficult because the legends are built up in a different way. Physiography as 
expressed in colourtone (hue, value, chroma) and colour pattern (texture) have 
e extreme- 
been used for the interpretation of the ERTS-1 image on the colour composite 
the fact 
in conjunction with field work. Soil characteristics in conjunction with lithology 
nagery 
idjacent 
; but it is 
have been used as differentiating criteria with the soil map of Spain. The results 
and discussion of this comparison are to be found in table 2. 
Conclusions reveal that the interpretation of ERTS-1 imagery was successful with 
tzite- 
respect to both physiography and lithology for approximately 1/3 of the total sur- 
ifferen- 
2 
vey area of 25, 000 km , covering Alluvial valleys (A), Aeolian deposits (S), 
;rey tones. 
ly good in 
units is 
Complex of rallas, miocene clay, metamorphic and sedimentary rocks (R), and 
Miocene clay (M). 
The interpretation was moderately well done in approximately 2/3 of the survey 
5 at least 
area (physiography: good; lithology: poor) covering the following areas mostly 
developed on metamorphic and igneous rocks: undulating (C), undulating to 
scales 
rolling (O), rolling to hilly (B), and steep hills and mountains (L). 
4, 5, 
d 4 has 
The ERTS-1 interpretation failed completely in approximately 5% of the area 
(Soil Map of Spain: units 3, 8, 9) covering parts of the undulating, rolling, and 
hilly areas developed on metamorphic and igneous rocks (B and C). 
* 
Instituto Nacional de EdafologiSi y Agrobiologist del C. S. I. C. , Madrid, 1966.