Corten, A Survey Navigation System 
5 
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. 
Temperature T 
Corrected outside air temperature ......... COAT 
Airplane’s speed in general V 
Airplane’s speed with respect to an air mass coordinate system . . . TAS 
Airplane’s speed with respect to a ground coordinate system . . . GS 
Wind velocity vector WV 
Wind speed WS 
Hour of time ............. hr 
Second of time sec 
Radians, 180 degs/jr, number of sexagesimal degs per radian, 57.3 . . p 
Drift, navigational drift angle D 
Survey drift correction angle .......... <3 
Airplane’s heading H 
Airplane’s course Co 
Airplane’s track • • T 
Bearing relative to airplane . . . . . . . . . . .. B 
True direction or bearing . . . . . . . . . . T.. 
Magnetic direction or bearing . . . . . . . . . M.. 
Compass direction or bearing . . . . . . . . . . C.. 
Relative direction or bearing . . . . . . . . . . R.. 
e.g. True heading ............ TH 
Relative bearing RB 
True course . . . ■ . . . . . . . T Co 
Magnetic variation ............ VAR 
Compass deviation ............ DEV 
Distance to go or distance gone DIST 
Rate of turn ............. r 
3 degs per sec of time ........... rate 1 
Internat. standard atmosphere ......... ICAO atm. 
Atmospheric pressure corrected to msl according to ICAO atm QNH 
Atmospheric air pressure .......... V 
Sea level air pressure P ms i 
Milibars .............. mb 
Geographic latitude ^ 
Air radius of coordinated turn with respect to an air mass coordinate system R 
Diameter of reciprocal turn with respect to a ground coordinate system . M 
Factor converting R into M, = M/R ........ m 
Displacement necessary to obtain A by means of M if A < M . . . d 
Intermission — or distance interval — necessary to obtain A by means of 
M if A > M i 
Interval, time duration between consecutive exposures A t 
Base ratio ............. B/Z or b/c 
Width ratio ............. A/Z or a/c 
Speed ratio ............. GS/Z 
Wide angle (camera or angular coverage) WA 
3. Survey navigation functions performed. 
Navigational functions can be performed by using basic flight elements in a systematic 
way. 
3.1 Absolute flight altitude is established and strictly adhered to by means of barometric 
altimetry applying all appropriate corrections: this determines photo scale and line spacing.