Potcoava, Mariana - Camelia
Figure 2. Examination of various features of the area with different band combinations: 3-2-1; 4-5-3; 5-3-1.
The LANDSAT - TM4 (700 - 1100nm) is useful for delimit the vegetation area of water aria because the contrast is
enhanced between areas (figure 3).
Figure 3. The accurate delimit of the water body of vegetation area
2) ERS-1 SAR
ERS - 1, the earth observation satellite of the European Space Agency (ESA) carries a C band (wavelength = 5.3 cm),
VV polarisation and 23° average indice angle SAR which acquires images of the earth's surface in all meteorological
conditions.
In the SAR image (figure 4), the urban area is well imaged and the density of the built-up area can be assessed by the
strength of the back-scattered signal. In contrast to the optical image, highways, large roads and avenues are presented
as dark lines. Bridges and railways on the contrary are imaged mostly very bright due to the dielectric property of metal.
In the full-resolution subsection of the image the patchwork of the fields is well visible. The colours of the fields depend
on the changes in surface roughness occurring between the acquisition dates. Data acquired in spring and summer are
used to identify the crop type; a methodology similar to that applied with optical data. However it has been reported that
also data acquired in the winter are of great interest, since they reveal the work performed which is often indicates the
preparation of the fields for a certain crop. This permits at a very early stage in the year to assess certain crop types and
estimate their extent. It is obvious that such data application must be based on good knowledge of the time and type of
field preparation. Adequate ground survey needs to be available as a starting point.
Figure 4. Representative area of ERS -1 SAR colour composite image, Colentina River, from 3 June 1992 -red, 25
November 1992 - green, 30 December 1992 - bleu
1188 International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B7. Amsterdam 2000.
