490 
SYMPOSIUM PHOTO INTERPRETATION, DELFT 1962 
Fig. 1. Schematic section showing the relationships of the A, X, Z and B sites to the present 
landform 
led to the selection of the “X” and “Z” sites almost all of which correspond 
in situation with the “A” sites. 
A total of 46 sites were checked by pitting to a depth of five feet wherever 
possible, and 66 pits were made. The deposits were graded as follows: 
Grade 1 “Gravel” deposits complying with standards of table 1 greater 
than T6" thick. 
Grade 2 “Gravel” deposits complying with standards of table 1 less than 
1'6" thick. 
Grade 3 Slightly laterised sands. 
Grade 4 No latérisation. 
The grading of the 46 deposits is shown in table 2. 
Table 2 
Deposit Type 
Grading 
1 
2 
3 
4 
Total 
A 
1 
2 
1 
6 
17 
Z 
6 
0 
2 
3 
11 
В 
4 
2 
3 
1 
10 
X 
4 
0 
3 
1 
8 
Total 
21 
4 
9 
11 
46 
The A and B deposits are those of the initial interpretation and the X and Z 
deposits of interpretation subsequent to initial field checking. The difference 
in degree of success between the A and the X and Z types is due mainly to the 
different criteria used to select them. 
Vegetational criteria are discussed briefly since neither author can comment 
adequately on them. However, it is interesting to note that in the “B” sites 
there occurs a white speckling, often due to the presence of a scrub identified as 
Eriosema engleranum (understood to be characteristic of overgrazing). In some 
areas the speckling may be due to small anthills indicative of retarded drainage 
or hard-pan. Over many “B” sites there is a greyish grass which gives a “blur 
red” photo-tone. The diagnostic value of the two vegetation types cannot yet 
be assessed, but it is possible that they indirectly indicate a particular soil 
condition characteristic of an impermeable sub-surface layer. On the inter 
fluves, a species of Monotes is reported to be almost 100% diagnostic for laterite.