5 
Experience shows that only the renown survey contractors and some well-specialized na 
tional mapping agencies are able to produce high quality results. 
Survey navigation is very often based upon the personal experience of the crew rather 
than on a systematical approach. Although there exist a few flight organisations capable 
to produce excellent navigation of a large area of unmapped terrain, we consider it very 
useful, specially for organisations with less experience, to make use of a good survey naviga 
tion system. Ir. F. L. Corten, Head of Branch C (Air Photography and Survey Navigation) 
has established such a system based on the functional analysis of the appropriate naviga 
tional elements. These are: the establishment of absolute flight altitude, establishment and 
correction of aircraft heading, application of drift and drift correction angle, use of sighting 
angles, estimation of relative terrain elevations, application of the line of sight, application 
of rated turns with the use of the ITC Survey Flight Slide Rule to compute the turns [24], 
application of deduced reckoning navigation, of Doppler navigation and other elements. 
Each of these can perform a specific function in survey navigation and the system is designed 
in such a way as to make optimum use of their functional interconnection. 
The ITC Survey Flight Slide Rule will be available on the Congress Exhibition. 
In the ITC physical laboratory research has proceeded in the field of Applied Optics 
and Image Engineering, not only theoretically but also experimentally [39]. With the 
ITC sinewave test target, the imageing quality (expressed in Modulation Transfer Func 
tions) has been determined of: 6 different stereoscopes; 15 plotting instruments; 3 reduction 
printers; 3 enlargers and rectifiers; 2 contact printers, and some cameras. This activity 
concentrates on those sectors in aerial photography, to which the ITC has easy access 
(various types of instruments) and where ITC is asked for advice, for instance to determine 
the quality of exposed aerial negatives or diapositives. The current ITC research on pointing 
and pointing accuracy is connected with this last item. 
A good example of “Applied Optics and Image Engineering” is the overall study of the 
performance of stereoscopes from the point of view of the user. It resulted in provisional spec 
ifications for mirror stereoscopes, which have already proved useful for manufacturers [38]. 
Such a study is going on for dodging and dodging printers; on both items research and 
testing was carried out in the past four years. Specifications for dodging printers can be 
given now, but, although good dodging surely offers advantages if applied in the proper 
situation, the main drawback is not the dodging performance, but simply reliability, adjust 
ment and operation. 
The experience with electronics in darkroom equipment (and not only there) have 
just been bad, these last years. Therefore the ITC has not hesitated to stress to the com 
panies the importance of delivering foolproof, reliable equipment with sufficient data 
on performance and adjustment, which can be operated by photographic technicians. 
CHAPTER II. PLOTTING INSTRUMENTS 
Again the number of plotting instruments in this country has increased considerably during 
the past four years. The Cadastral Service obtained, in addition to its Stereoplanigraph C8, 
the Galileo Santoni Stereosimplex III B and the Wild Autograph A8. The choice fell on 
the Stereosimplex III B because this instrument also takes the convergent photography 
taken with the Zeiss RMK convergent 18 X 18 cm, although the application of this type 
of photography has decreased in this service. The Survey Dept, of the Ministry of Transport