ESS
(490)
graph contour-lines obviously render the feature well, details are better repre-
sented than by the 10 m contour interval of fig. 2a. Irregularities of contour
lines correspond in the main to real irregularities of terrain forms. In the con-
trary the contours of multiplex: the forms of contour-lines are considerably
disturbed, they are affected by the “differential uncertainty". The error my =
1,35 m 1s a substantial part of contour interval Ah = 5m, also the horizontal
distances of contour lines are affected in irregular manner. Where the slope of
terrain is uniform the disturbed contour lines show steep slopes and flat places
by turns. The result of multiplex-measurement is obviously incorrect.
But it is possible to improve this incorrect result by estimating and thus
Multiplex Multiplex
Dfferenzrelle Unsicherheit guf 6eserfigf. Oifferenzielle Unsicherheit schlecht Geseifigf.
Differential uncertainty properiy eliminated. Differential uncertainty not well elrminated:.
G5 735m Ah 3.72
Fig. 4b
eliminating the differential uncertainty. When measuring the contour lines the
operator sees the forms and slopes correctly, he can also study them with the
aid of a separate stereoscope. The stereoeffect shows them correctly and very in-
tuitively without any differential uncertainty, the latter occurs only when plot-
ting the contour lines which is done separately one after the other. — Using this
correct stereoscopic impression the operator is able to draw the final contour
lines by estimation, he smoothes down the irregularities obviously caused by in-
correct measuring, but he should be careful not to eliminate also the real forms
corresponding to the terrain. — Compensating differential uncertainty is a
responsible task, one can improve much but also lose plenty of correct forms.
In most cases the latter may occur.
Fig. 4a and b give an example. In fig. 4a uncertainty is properly elimi-
nated, in fig. 4b this is done not so well, steps in the trough do not correspond to
the reality.
It is of great interest that the contour interval Ah = 5m in fig. 3b (Multi-
