The most important quality of the subject photographed 
which determines exposures and development is its maximum 
and minimum brightness. We have as yet no instrument to 
measure these. In consequence usual procedures are based 
extensively on guess. 
A Survey Navigation System 
SKELETON OF SURVEY NAVIGATION 
by F. L. CORTEN, 
I.T.C. Delft 
CONTENTS 
1. Introduction. 
2. Navigational elements used. 
3. Survey navigation functions performed. 
4. Survey navigation as a system. 
5. Reference literature. 
ABSTRACT 
Medium and small scale photography is mostly carried out over areas where good maps 
do not exist. Survey navigation then presents special problems which cannot be solved by 
general navigation methods. 
This article describes the principles of a survey navigation system based upon the 
use of conservative flight elements forming a coherent system. This is presented as a 
skeleton of functional relations. 
1. Introduction. 
Survey navigation can be based on the use of existing maps only if they are good and 
sufficiently reliable; in all other cases the survey flights must be based on no-map naviga 
tion which is general practice on nearly all medium and small scale photography. 
Special problems must then be solved because survey specifications call for a much 
higher accuracy in flight than aircraft-plus-instruments are designed for, and than pilots 
or navigators are trained for. Also, radio navigation cannot be applied and all approach 
navigation aids are useless. 
This is the explanation of the well-known fact that any attempt based only on good 
general navigational principles and experience is bound to fail. Therefore, some survey 
contracts and government mapping organizations have had to develop navigation methods 
of their own. Some of these are straightforward, good and sound [see reference literature 
1.. . 5], and produce excellent results. Often they are based on special requirements or are 
tuned to the use of a particular type of aircraft or instrumentation. In many other cases 
also, survey navigation is not based on a logical system but is made to fit the personal 
habits of a navigator experienced in a certain type of survey or country or aircraft. It is 
clear that any changes — be it personal or instrumental or environmental — will bring 
such flights to a complete failure. 
In this publication, a logical method of survey navigation is outlined. Starting off 
from a number of conventional flight elements and also including some modern navigation 
methods, the basic functional relations between these elements are used. The functions are 
then combined to a coherent system. 
In aerial survey, we must look ahead to make use of all future possibilities for impro 
vement: at the London congress the author has presented a review of these possibilities 
[6]. On the other hand, the world of today needs production, of optimum quality and in 
high efficiency, using the flight elements which are available now. This need is the back-