2. Improvement of aircraft control 
On a worldwide scale, aerial photogrammetry is predominant 
ly carried out in small aircraft with visual navigation to 
follow the given photographic flight routes, while 1arger 
airplanes with instrumental navigation are mainly used for 
electronic surveying systems, such as scanners and side- 
looking radar. This is due partly to the recording prin 
ciple and partly to the ratio between the investment re 
quired for the aircraft and that for its instrumentation. 
It is well known that the high prime costs of an automatic 
precision navigation system pay off rapidly, thanks to its 
outstandig qualitative and economic advantages. This can be 
substantiated by the fact that exact route navigation and 
stability of the flying attitude reduce side lap and thus 
the number of flight strips. In addition, expensive repeat 
flights can be minimized. 
An advanced navigation system has to serve two fundamental 
tasks in airborne remote sensing, viz. 
- ensure highly precise and reliable fligth at reasonable 
costs, and 
- supply the data of exterior orientation (station coordi 
nates, flying attitude angles) for the on-line control 
of imaging system and their synchronous recording by 
that system on the remote sensing data carriers. 
According to INTERFLUG investigations, the first problem 
requires the following accuracies of exterior orientation 
for a block of exposures, concerning the path of fligth 
along a route relative to its middle line or concerning the 
mean attitude angles and the routes of a block of 
exposures relative to each other: 
- Relative on-line position accuracy (depending on flying 
height h : 
Planimetry Ax , Ay = n • 15 m; h < 2 km : n = 1 
Elevation Az = n * 20 m; h = 2.. 4km : n = 2 
etc . 
- Dynamic on-line angle variation at any flying height: 
angular velocity about each of the three axes (pitch, 
roll , yaw) < 0.2°/s 
- Relative on-line accuracy of attitude at any flying 
height: (pitch angle, roll angle, yaw angle) < 0,5° 
for photographic and matrix camera, and < 0,2° for line 
scanners and side—looking radar 
The position accuracy can be materialized by the aircraft 
alone, while fine stabilization down to the residual values 
mentioned above is possible, after prestabilization by a 
flight regulation system, by means of a platform /4/ with 
dynamic attitude stabilization for the respective sensing 
system. 
A navigation system meeting such demands might be a 
satellite-aided global positioning and navigation system, 
such as GLONASS (USSR) or GPS-NAVSTAR (USA). This is 
expected to essentially improve the quality and economy of 
remote sensing and particularly its photogrammetric branch. 
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