4 
Photogrammetria, XIX, No. 6 
ground of the existence of the regular course of education and training in survey naviga 
tion and aerial photography at ITC. It is also the background of the skeleton of survey 
navigation presented in this article. 
2. Navigational elements used. 
In modern aviation a large number of navigational elements and methods is available. 
For the survey of poorly mapped areas, however, preference must be given to methods 
which are airborne, i.e. methods which are self-contained and independent of ground 
stations. In this way radio ranging, approach navigation and similar methods cancel out 
for aerial survey. 
2.1 Elements used. 
In basic survey navigation, conventional flight elements are used and some electronic 
data are applied; most of them are measured or obtained during flight and are introduced 
into the navigation system as described in the subparagraphs of par. 3 under ‘Input’. 
2.2 Notations and symbols in survey navigation. 
The relations between the flight elements are expressed in navigational formulae; the 
symbols used therein are the following: 
Camera principal distance .......... 
Terrain photo coverage size .......... 
Camera image size ............ 
Nadir or plumb point in terrain ......... 
Air base .............. 
Photo base ............. 
Flight line spacing (lateral air base) 
Lateral photo base ............ 
Actual flight line spacing as determined by ground nadir points’ positions 
(or true track TT) 
Angles in horizontal plane (such as heading changes, etc.) Note: for drift 
angles and drift correction angles special symbols D and <5 are used . 
Angular values along-track, angles in the vertical plane of flight line (such 
as collimator dip, airplane pitch, etc.) ....... 
Angular values across-track, angles in the vertical plane across the flight 
line (such as angle of bank, etc.) ........ 
Camera axis’ inclination in arbitrary direction, with respect to the vertical 
Longitudinal terrain overlap fraction ........ 
Longitudinal overlap, forelap .......... 
Lateral overlap, sidelap 
Relative terrain elevation as fraction of Z 
Absolute datum, mean sea level ......... 
Reference elevation ............ 
Elevation of any terrain point n over msl ....... 
Reference elevation over msl .......... 
Camera station’s elevation over zero datum ....... 
OR: airplane’s true altitude above msl 
Flight height over reference .......... 
Terrain clearance over point n ........ 
Photo scale number 
Time, instant or hour of the day ......... 
Time, duration between two time instants 
S 
s 
N 
B 
b 
A 
a 
K 
v 
a 
P 
v 
U 
u 
V 
w 
msl 
ref 
K 
K 
z 0 
T ALT 
z r 
Z n 
E 
t 
At