the Central region of Spain, southeast of Madrid (Figure 1), over an area
of 2,250 sq. Km.
Geologically, the study area belongs to the tectonic basin of river
Tajo filled with Neogene sediments. They are formed by a variety of deposits
(sand, clay, silt, gravel, gypsum and limestone). The climate of the region
is typical Mediterranean with dry warm summers and moderate winters. On the
surface of the high limestone plane, the climate is slightly warmer and more
humid than that of the valleys, with an average precipitation and temperatu-
re between 378-535 mm and 12.8-14.0 °C respectively per year. The moisture
regime of soils is xeric and the class of soils temperature regime is mesic. |
|
A Sw sh al ww. NA
The most important landforms found in the area are: 1) Alluvial valleys,
and lower terraces, mainly along the Henares, Tajufia, Tajo and tributary ri-
vers, that serve as the main drainage of survey area. These valleys appear
covered by vegetation in the image we are stuying. 2) High limestone plain,
with processes of erosion and sedimentation on the surface which modify the
physiography of the primitive structural surface, 3) Hillside scarpments for
med by the erosion of the limestone plane and covered by calcic pebbles, fa-
llen rocks and gross materials surrounded by and sandy clay loam matrix.
4) Low hills with plabe top characterized by and abundance of gypsum and li- | :
mestone rocks, ssociated with eolian deposits.
The soil surface reflectance is the result of the soil profile, but al-
so the result of the surface conditions (texture, colour, slope, vegetation
coverage, etc). Soil spectral maps, are the synthesis of soil conditions at
a given date and a particular landscape. These circunstances are sufficiently
important to justify the use of Landsat data in soil inventories including
associations with dominant soils.
2. MATERIAL AND METHODS
Landsat MSS image number 2223-10135 collected on September 2, 1975,
was used for this study. This scene was selected because at the time most crop-
land was in a bare soil state, with the exception of small cultures (orchards,
olive groves and vineyards).
A rectangle was selected from the original digital tape between lines
909 to 1,910 and pixels 1,121 to 1,630. This subscene was referred to UTM coor-
dinates by means of seven ground control points and a second order mapping po-
lynomial, obtaining a geometrically corrected image with pixels of 80 x 80 m.
The geographical coordinates of ground control points were selected from topo-
graphic maps at scale 1:50.000.
With the purpose of comparison between spectral soil maps derived from
analysis of Landsat data and conventional soil maps, the following maps were
used: 1) Soil maps at scales 1:1,000,000 and 1:400,000, 2) Aerial photogra-
phy at scale 1:30,000, 3) Geologic map at scale 1:200,000, and 4) Soil map
at scale 1:200,000, unpublished.
The digital analysis was conducted with the help of the interactive sys-
tem ERMAN-II and displayed on a color monitor for obtaining, modifying and ve-
rifying results.
