-3- 
be bridged. In odd cases, however, where the accuracy of aerotriangu- 
lated elevations is, for some special reason, the critical value, the 
mbd charts and equations have to be used in a slightly different way. 
Details on this point will be given later in an example. 
Figures 2 and 3 show two universal mbd charts developed at the 
University of Illinois for the cases of 60% and 70% longitudinal over 
lap, respectively. Figures 2-a and 3 -a are intended to supplement 
Figures 2 and 3 for the small range of/lj_| and mbd. Charts 2, 2-a, 3 and 
3-a are worked out with the following restrictions in the different 
parameters: 
1. Accuracy requirement (mean square error) in planimetry: +0.02 in. 
(±0.5 ram) measured on the publication scale of the map. 
2. Accuracy (mean square error) of measurement of parallax in a 
stereoscopic instrument: +0.0004 in. (+0.01 mm) (in image plane). 
*+ 
3« Relative Orientation: According to Bachmann 
4. Aerotriangulation: Instrumental conjunction of successive photo- 
graphs without auxiliary data , generally termed "Aeropolygon". 
5- Ground Control and Adjustment: Cross Bases Method 
6. The chart could be used for aerial cameras with principal distance 
ranging from 3 in* ** *** to 12 in. 
* A summary of this method is given in the Appendix. For complete 
details, see Bibliography Entry No. 1. 
** Better known by its German name "Folgebildanschluss”. For details 
see Bibliography Entry No. 2. 
*** See Bibliography Entry No. 5 or 9. 
+ For all practical purposes, however, any other method could be 
used. Experience has shown that there is no substantial difference 
in accuracy between the different methods.