a 
3050 
3) 
es 
^ 
Technical remarks concerning the proposed system 
The mapping system can be divided into two principal phases, the production 
of photo base maps (Phase A) and their subsequent perfection to the stage of 
multi-colour line maps (Phase B). 
A brief review is now given of the main technical characteristics of the 
system, from which it should be clear that the system has been designed to 
meet the specific needs of the developing countries, 
Phase A 
Superwide angle photography at a scale 1:100.000-1:120,000 yields, in 
connection with analytical radial triangulation and orthophoto production, 
sufficient planimetric accuracy for topographic maps at scale 1:50.,000, 
Height accuracy (if Laser APR profiles are provided in the lateral overlaps) 
will be sufficient for 20m contour intervals if dropline charts are prepared 
and for 10m contour intervals if contouring is carried out in photogrammetric 
plotterso 
Aerial photography has to be taken using & stabilized mount, to yield 
sufficiently vertical photography for the designed employment of analytical 
radial triangulation. 
Assuming that no complete primary geodetic control in planimetry exists, and 
in order to avoid the long delay caused by this operation, only a few wide 
spread astronomic stations have to be determined along the perimeter of large 
blocks. Although the absolute accuracy of these data will be low, they will 
suffice as preliminary planimetric control. If only a few stations are used 
at distances of 100-150 km from each other, the relative accuracy of the 
resul ting maps will not be reduced. 
If at a future stage, final geodetic primary control is obtained, a re-adjust- 
ment of the data of the analytical radial triangulation can be carried out 
and the resulting corrections can be used to construct new co-ordinate grids, 
without any necessity to change the actual topographic maps. 
Radial triangulation is employed, because only planimetric coordinates of 
minor control have to be determined and it is faster and considerably 
cheaper than spatial aerial triangulation. (See also 6.). 
Minor control in height is provided by (Laser)-APR profiles, flown at low 
flying heights along the lateral overlaps of the aerial photography. 
Cross profiles have to be flown &t regular intervals (30-60 km) to allow for 
a net-adjustment of all profiles, For the adjusted APR height, an accuracy 
of 1-2 m (standard deviation) oan be expected.