104 
construction and particularly by the possibility of introducing 
the corrections which are necessary in the terrain with large 
slopes. It is well known that with the narrower strips the 
greater number of strips must cover one orthophotogram. In most 
instruments the width of strip /slit/ from 2 ram to 8 mm is used, 
howewer the slits of 2/3 mm to 40 mm are also in practice. 
Speed of scanning is conditioned by the device used in a given 
profiling process system, but in the instrument controled by 
the man observer it depends also on his ability and knowledge. 
In some systems it is conditioned by the scale difference between 
the original photo and orthophoto image. If the difference is 
greater the slower speed of orthophoto reproduction /rectifica 
tion/ is noticeable. It is caused by the real time necessary 
for rectification on the one hand, and by the limitation in the 
possibility of driving measuring mark in nonautomatic systems 
on the other. It decreases in the same ratio as the orthophoto 
scale inereases in relation to the original photo scale /in 
"on-line” systems/. In "off-line” system the speed of scanning 
depends on the way of the terrain model cross-3ection registra 
tion. It can be presented either in an analogue or numerical 
form. The speed of profiling when the man operator controls the 
work depends on the lay of the land and is variable from 0 # 7 mm/s 
to 8 mm/s /in scale model/. Table 1 shows the time required 
for profiling purposes using C-8 Zeiss Oberkochen stereoplani- 
graph and SG-1 storage unit [3] • 
Table 1 
Time required for profiling 
Model scale 
1:10 
000 
1:5000 
Increment AX /= slit width/ 
2 mm 
4 mm 
4 mm 
'time in hours 
Model orientation, recording 
♦ 
of control and check points 
2.0 
2.0 
2.0 
Connection of SG-1 
0.5 
0.5 
0.5 
Profiling and profile storage 
3.0 
1.5 
• 5.0 
Preparations, ect. 
1.0 
1.0 
1.0 
Total man hours 
6# 5 
5.0 
8.5 
Orthophoto systems are equipped with devices changing the speed 
of profiling. This speed can reach the value 15 mm/s. It is 
a very low speed considering the fact that the devices based cn 
the automatic .image correlation can profile with the speed of 
10 cm/s. However, we have to notice that in the average profile 
of a terrain with moderate or strong undulating /created on 
photos in large or medium scales and in the size of 23x23 cm/ 
along the full Image size /perpendicularly to the base/ 200 or 
300 points are needed. Numerical registration of coordinates in 
this case is rather difficult. Registration devices based on 
magnetic-type /Kennedy 1600, Dygidata 1400 or Recording Designes 
10000/ can register two coordinates /Y,Z/ at the speed of 30