I. INTRODUCTION 
Developments in aerial photogrammetry have always aimed at 
perfecting techniques so that photogrammetric surveys could be 
carried out exclusively from airborne data and without the neces- 
sity of independent measurements on the ground. In terrestrial 
photogrammetry, position and orientation of the camera stations 
is determined by "auxiliary surveys" performed on the ground 
but remote from the photographed object. The idea of control- 
ling camera stations rather than establishing control points on 
the photographed object seems to be as old as the science of 
photogrammetry. In early application of aerial photogrammetry, 
ground control points were essential in each stereomodel. Later, 
aerial triangulation methods, whether analogue, semi-analytical 
or analytical, combined with sophisticated adjustment techniques, 
permitted bridging between known geodetic control points and 
decreasing the dependence of photogrammetry on ground control 
surveys. 
Introduction of airborne auxiliary instrumentations which 
determine the position and orientation of the aerial camera at 
the moment of exposure is, therefore, a logical extension of 
this trend in photogrammetry. We endeavour to become independ- 
ent of ground control and to devise a mapping system which 
could virtually eliminate surveys on the ground for the purpose 
of photogrammetric mapping. Such development will surely have 
wide ranging technological and economical implications. I am 
not advocating that monuments on the ground with known positions 
and elevations are not necessary. On the contrary, they are 
essential to the users of the survey effort but I believe that