- 4 =
b. À second factor is the aim of the survey. This aim is determined by purely
technical factors, and also by factors which can have a political or socio-
economic character.
What is the aim of the different phases ?
An exploratory survey is done to localize areas with potential possibili-
ties for development and to exclude areas for further investigations.
A reconnaissance survey is carried out to see whether it is worthwhile to
continue and to see in which general direction the development should go.
From the semi-detailed survey the decision should be made whether the pro-
ject can be executed,
The detailed survey is done to obtain data for ihe execution of the pro-
ject.
c, Available time and financial means were given as answers in some cases. e e
4. Size of ihe smallest unit
The answers to this question were far from uniform. The question was not re-
levant for the civil engineers, the sociologists and the economist because
they generally do not plot characteristics which can be expressed in area-
units,
6 experts (2 geologists, 2 pedologists, 2 geomorphologists) gave the answer
that the unit to be mapped should have on publication scale at least a width
cf 1-2 mm for elongated areas, and more circular areas should be at least
4 x 4 mm on publication scale. If we express this for the different phases
in the actual size in the field, this means:
elongated areas / circular areas
exploratory larger than 500 - 1000m / 2000 x 2000m
reconnaissance larger than 100 - 200m / 400 x 400m \ |
semi-detailed larger than 25 - 50m / 100 x 100m e o
detailed larger than 10 - 20m / 40 x 40m
2 specialists interviewed stated that very important objects which are small
for representation on a map, should be given either as a symbol or should be
drawn in an exaggerated form.
One soil surveyor mentioned that the question of minimum size is ónly rele-
vant for those units which may have an important influence on future deve-
lopment. His smallest unit would then be about 1 sq. cm. on publication
scale.
AERIAL PHOTOGRAPHS
1. Aerial photographs as & tool for surveys
Nearly all experts answered in the affirmative, although there is a con-
siderable difference in ideas regarding the intensity of use of the photo-