of terrain. In flat open terrain, with little woods and trees, as in Western Holland, there 
are as an average 200 ground control points per 1000 sq. km. In the flat areas with more 
trees and less triangulation points are triangulated by means of a radial triangulator (see 
CHAPTER III). Supplementary horizontal and vertical control in the hilly part of the 
country is only in a few cases determined by aerial triangulation. Because of the density 
of the available geodetic control almost all the control points can be more easily and 
cheaply determined by ground survey. 
The existing method of determining, ground control as well as minor control points, 
is at present entirely satisfactory, and no intention exists to change this in the near future. 
The new radial triangulator Wild RT 1 with which several tests have been carried out, 
gives very satisfactory results. Since 1958 the Topographic Service have applied the 
scribing technique for the final drawing of its base map 1 : 12.500. It has also been found 
here, that this technique can save time and gives very fine results. The Topographic 
Service considers it to be very important to develop efficient methods in scribing and 
stripping techniques because of the fact that this is in general a time consuming part of 
the mapping procedure. 
With regard to checking, the Topographic Service adapted a method in which every 
step in the process is checked by the next one. The accuracy of map details is thus contin- 
uously assured during the whole process up to the printing. Several tests of the base map 
and colour separations are carried out with the aid of high precision coordinatographs. 
Field reconnaissance is carried out by skilled topographers just before the final drawing 
of the base map. This assures the completeness of the map. During the period covered by 
this report the method of scribing on plotters was tested but it was not put into practice. 
TABLE 7 gives valuable information on the distribution of the time and cost of the various 
elements of the mapping procedure in the Topographic Service. 
IV.b. K.L.M. Aerocarto and Survey Department of Rijkswaterstaat 
It is not possible to give a systematic list of the details regarding this part of the Nether- 
lands’ map production, as the commissions for small scale mapping are so varied both in 
scope and execution. This is due to the fact that this kind of topographic plotting was 
carried out by these organizations mainly for foreign countries and for Netherlands areas 
overseas. We can mention that in general the following scales are used: 
Publication scales bi: 20.000:...1, 725.000: 1.:,100.000 
Plotting scales 1:2:20.000; . 125,000; 1:::100.000 
Scale of photography 1: 25.000; 1 : 30.000; 1 : 40.000; 1: 60.000. 
The types of cameras used are: Zeiss P 10, Wild R.C 5, Wild RC 5a, Williamson OSC II 
and Trimetrogon. The types of plotters used are: Wild Autographs A 6 and A 8 and the 
Kuipers L.S.P. plotter. 
The tolerances are so entirely different that it is of little value to state for instance that 
in general for planimetry for maps 1 : 20.000 and 1 : 25.000 this is between 10 and 15 m. 
For altimetry, depending upon the available ground control it can be expressed by the 
formula that in 809, of the mapped area the error should not exceed half the contourline 
interval. In the latter case there must be vertical control in each fifth model. 
There is also a wide variety of ground control namely astrofixes, triangulation points, 
local base lines and points from existing maps, for instance hydrographic maps. In 1959 
the survey of a large overseas area started with the use of Decca controlled points. 
The density of such ground control is different. In some cases bridging had to be carried 
out between astrofixes at distances of at least 80 km. In the Decca program, mentioned 
above, the distances between Decca points are between 15 and 20 km. 
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