most critical limitations of these methods do not lie in the electronic instrumentation but in 
the uncertainty of the exact propagational velocity values. 
To date, the best accuracy results are obtained by means of Aerodist, although its range is 
limited to approx. 200 km. For planimetrie control determination over longer distances, 
Shoran or Hiran or Shiran or Decca must be used. 
Propagational velocity being = 299 792. 5 + 0.4 km/sc., in vacuo, corrections must be 
applied for 
- Atmospheric air pressure, 
- Air refractive indices, 
- Relative humidity, 
-Air temperature, 
- Slant range air pressure gradient, 
- Conductivity of terrain, 
and other influences. 
The accuracy of this basic element is determined by the degree of knowledge about the 
actual atmospheric and terrestrial data. 
Performance of systems. 
Using electronic distance measuring equipment, different applications are possible: 
System number 
Description 
Random errors in meters position 
DIST 1 
Line crossing, producing ground- 
to-ground distances with standard 
error. 
approx. 1 m at 150 km distance. 
The error varies approx, with 
the square root of the distance. 
DIST 2 
Exposure station nadir, with 
adjusted verticality and known 
flight height; standard error. 
high for each single unadjusted 
nadir. 
DIST 3 
Airborne trilatération (no 
reliable data available to author). 
DIST 4 
Multiple photography secondary approx. 5 m at 150 km distance, 
control point positioning, standard Error varying distance, 
error. 
1.000.000 
COST OF 
PLANIMETRIC 
INFORMATION 
enveloppe 
/ 
PERFORMANCE 
planimetrie accuracy 
100.000 
100 
10 
1 
meters 
0.1 
The investment varies per system and per mode of application, as well as the performance 
of the systems and modes.