capacity. At this time the only alternative to achieve adequate progress
rates in surveying and mapping in many countries appears to be to increa-
se the degree of efficiency of these operations in the framework of the
presently available means or of relatively modestly increased means in the
near future.
Decisive factors to achieve this as far as the mapping sector is
Concerned are the map content on one side and map revision on the other
side. These two factors are so important that we feel it is essential to
elaborate more on their impact on the economy of mapping.
A map is a portrayal of terrain features of various degrees of per-
manency. The amount of permanent features, particularly in urban areas,
decreases rapidly as a function of time as is illustrated in Figure 1 (the
curve is the inverse of a geometric progression as permanent features in-
crease with the inverse of the population increase which follows a geome-
tric progression).
Amount of Permanent Features on the Ground
Time
i |
20 30 40 50 years —
Figure 1: AMOUNT OF PERMANENT FEATURES ON THE GROUND
AS A FUNCTION OF TIME.