ces.The interpretation of accelerated erosion is made in view of the prepara 
tion of erosion maps which can he used for land classification and for 
conservation planning. 
THE PHOTO-INTERPRETATION OF ACCELERATED EROSION 
In order to extract the most information from the aerial photographs 
for a soil survey,many interpretation-elements are used (Buringh i 960 ,Vink 
1968 ).For the study of soil erosion largely the same photo-interpretation 
elements are used.This is logical Because of the strong relationship Between 
the pedogenetic factors and the factors determining soil erosion(Bergsma 
For the interpretation of soil erosion features the major interpreta 
tion elements and their aspects are:, 
-conservation measures 
Soil and suBstratum are interpreted as for soil survey. 
The presence of soil erosion features is mostly s 
indicate conditions of erosion hazard,and therefore guide the interpreter 
to the places in the landscape where he may expect erosion to occur. 
The greytone of the Bare land surface and low vegetation may of course 
show variations related to the colour and structure of the land surface and 
plant cover.Moisture content,sun position,photographic procedures also may 
cause greytone differences.Only some of all these differences serve the API 
of soil erosion features.(see also Goosen 1967).As greytone is a major 
API—element for soil erosion features,some general examples are given Below. 
X ) ABBreviation "aerial photo-interpretation" used throughout this text.In 
a similar way AP stands for "aerial photograph". 
Greytones and surface erosion (figure 1 ). 
Case A :Cross section A represents a common case of greytone pattern 
which is related to surface erosion.A light greytone is caused By erosion 
1970 ). 
Element 
-greytone(of Bare surface 
or low vegetation) 
Aspects 
-grade 
-texture(occurrence of greytone components 
of small size,usually less than 1 mm ) 
—pattern(occurrence of the larger greytone 
mottling) 
-inclination 
-shape 
-length 
-position 
-exposition 
-microrelief 
-type 
-density of cover 
-interruption of slope 
-colluvial terraces 
-slope 
-land use and 
natural vegetation 
-parcelling 
of greytone and microrelief.In most cases the other