4 
Survey navigation functions. 
- Absolute flight altitude and reference photo scale. 
- Altitude constancy, altitude differences between exposure stations. 
- Flight height above terrain or terrain reference elevation. 
- Air base distance and longitudinal overlap. 
- Mutual flight line distance and lateral overlap. 
- Flight line's azimuth. 
- Flight line's linearity. 
- Flight line's positioning and length. 
- Drift and crab. 
- Procedure turn transition to next flight line. 
Performance and cost. 
In all normal cases (including the more difficult ones) adequate performance survey navi 
gation can be carried out with relatively inexpensive equipment, if 
1. the aircraft is equipped for survey and carries the proper flight instrumentation 
2. the aircraft-plus-instruments system has been calibrated in flight to survey accuracy 
3. the appropriate survey navigation methods are applied. 
Addition of special navigational aids as doppler or inertial may not add much to the perfor 
mance under normal survey circumstances, but they may make it possible to carry out survey 
flights in those cases where it might be impossible otherwise. The graph illustrates the 
estimate investment for 
Standard survey navigational instrumentation. 
Education and training to survey navigator or to survey pilot-navigator. 
Doppler navigator plus computer. 
Inertial navigation including computer. 
Ground-based radio or radar navigation control. 
For uniformity of presentation, performance is expressed in lateral overlap spread. As a 
criterion for economy, a tolerance of + and - 5% side lap can be accepted. 
Performance and investment are represented in logarithmic scale.