TheImprovement ofTropical and Subtropical Rangelands

REGIONAL RESOUROE ASSESSMENT 89
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FIGURE 4-3a A mout d.iped for uiDc a conTentional 35 mm camera for
aerial photop'aphy. The portable mount clam~ to the door of a hich-wiDpd
licht aircraft (c.lDa). Here, the camera ia extended throUCh the left door
window where it caD be operated by a p...qer Mated iuide the aircraft. The
camera point. downward aDd ia protected in a mIlaO falrbac.
Use of Remote Sensing Data
Aerial PAoto,rtl.pA InterpretAtion Satellite images or aerial ph~
tographs can be interpreted manually by a trained analyst who
is familiar with the study region (figure 4-4). A. in any mapping
exerci8e, ~he objec~ive is to recognise areas ~hat are more or less
homogeneous in one or several properties. Using knowledge of the
region and the image characteristics, the analyst examines the image
and manually delineates are.. judged to be homogeneous. Are.. or
mapping units that appear to be related (fot example, sandy alluvial
fans) are labeled accordingly. These mapping units can serve
.. strata for subeequent sampling. Boundaries are determined, and
mapping unit descrip~ions are generated by e)famining large-scale
aerial photographs or by analyzing ground samples.
Single images are rarely used in remote sensing. The preferred
approach is to examine a number of images at 8Cales larger than
that of the bue map; larger-scale images are used to refine or label