-8- 
Figures 2 and 3 not only give mbd, "but they also determine the 
expected accuracy in elevations. Instructions for the use of the charts 
are given on the figures. 
Following the same basic ideas used to develop the charts, the 
following formulae for determining the Maximum Bridging Distance in 
* 
triangulated strips have been developed: 
/ \ \ M-f s 
mbd (feetj = 0.4 3 -p-—— 
and 
/ \ \ jU. f s 
mbd (^metersj =0-0 4 7 B\ ^ j. 
( 1 ) 
( 1') 
where 
S is the modulus of the map scale (map scale number). 
f is the principal distance of the camera (in inches or millimeters). 
B is the average length of aerial base (in feet or meters). 
Z=H is the average flight height above ground (in feet or meters). 
IU. is the tolerated mean square error in planimetry (in inches or 
millimeters) measured on the publication scale of the map. 
is the accuracy (mean square error) of the measurement of 
parallax in the image plane (in inches or millimeters). The 
value of /-t should be determined experimentally. In modern 
photogrammetric systems of average precision ¡JL> is in order of 
0.01 ram. (0.005 in highly precise systems). 
The expected accuracy (mean square error) in the derived elevations 
* 
of aerotriangulated points is expressed by the following formula: 
Q / / *"7 ^ 1 
= —¿T” -(U.3g - 1.25 N + 0.375 N 2 - 0.0625 N 3 + o.015625tjk)^ ( 2 ) 
D T 
* The derivation of these formulae is given in the Appendix. 
HHBBi