Fig. 2. Map B — 1:8000 (reduced 2/3) — com jiled by photogrammetric methods 
y 
fiom negatives at a scale of 1:18 000. 
considered to be the most accurate map of the four ones. The other 
three maps will be compared with this one. 
The aerial photographs at a scale of 1:18 000 and of 1:13 000 were 
taken with the camera Wild RC 5 15/23 and the photographs at a scale 
of 1:8 000 with the camera Wild RC 5 21/18. Contactprints at a scale 
of 1:8 000 and enlarged photographs at the same scale were prepared. 
These prints and photographs were then interpreted in mirror stereo- 
scope. The results were drawn and noted on the prints and on the photo- 
graphs. 
The stereoplotter Wild A 6 was then used for plotting of the 
maps B, C and D at the same scale of 1: 8 000 from the same diaposi- 
tives at a scale of 1:13 000. The models were absolutely oriented in rela 
tion to the same map A, but the differen! interpretations for the maps 
D, C end D were used when transforming the details from photographs 
to map. 
Two surveying technicians made the interpretation of the areas a and 
b for the maps D, C and D. They worked in a systematic serie with 
separate areas and separate photographs in order to avoid personal and 
systematic errors. 
The interpretation included the classification of ground with refe- 
rence to character of land, soil type, vegetation, and moisture, all noted 
in a code within the drawn sections on the photographs. 
2.4. The treatment of the primary material 
A system of squares of test lines was drawn identically on the four 
maps A, B, C and D. Within each square all the sections were put 
* - 
y * ^ 
x » 
X AY 
Le x 
+ + 
*« " 
+ * 
t +