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AERIAL TRIANGULATION WITH AUXILIARY DATA, BRANDENBERGER 99 
triangulation. This procedure yields auxiliary data for the drift by and the swing x and 
they can be used as conditions for the Strip adjustment especially with respect to the y- 
adjustment. The accuracy of the procedure depends on the length of the straight Jines 
which are transferred from the oblique photographs to the vertical photographs. It seems 
to be recommended to acquire more experience with this method and to gain more ac- 
curacy information. 
e. Shoran-controlled aiv stations. 
The planimetrie coordinates X and Y of air stations in an aerial triangulation can 
be obtained by Shoran and Hiran measurements respectively. This means that additional 
data is procured for the air base components bx and by. The accuracy of aerial trian- 
gulation with Shoran-controlled air stations depends on the accuracy with which the air 
stations are determined by Shoran. At present standard errors of about 5 to 10 m can 
be expected. A particular aspect which should be investigated more thoroughly is the 
economical aspect of this method. 
f. Aerial triangulation with horizon pictures, sun periscope, and gyroscopic recordings. 
In these systems auxiliary data is obtained for the lateral and longitudinal tilts œ 
and gy respectively. The methods involved are basieally not new and were already well- 
known in 1956. The problem encountered here is that it is not so easy to attain with these 
auxiliary data an accuracy of about 1¢ for and g which can be obtained from a direct 
relative orientation in a first order stereoplotting instrument. Also it seems to be that 
the accuracy of w and ¢ determination from horizon photographs considerably depends 
on the atmospheric conditions and horizon characteristics which might vary from country 
to country. The sun periscope method is basically less dependent on such local conditions 
and it would be doubtlessly interesting to obtain still more accuracy information on this 
method as is available up to now. There is no doubt that auxiliary data for w and ¢ from 
gyroscopic recordings are valuable too if a sufficient accuracy can be attained with this 
system. It seems to be that the system of gyroscopic recordings is still in a development 
state and that more effort is necessary to reach an acceptable accuracy for aerial trian- 
gulation purposes. 
g The method with independent geodetic controls. 
Although this strip triangulation method does not use airborne auxiliary data it is 
felt to be necessary to mention this method in the report for Subject 4 of Committee III 
since it is not very likely that this strip triangulation procedure will be covered by the 
reports for Subjects 1, 2, and 3 of Committee III. The basic idea in performing strip 
triangulations with independent geodetic controls is to use independent base lines, azi- 
muths and slopes at both ends of the strip and eventually somewhere between both ends. 
These independent geodetic controls are determined on the ground by geodetic methods. 
To perform the strip triangulation — for instance with a first order stereoplotting in- 
strument — the aeropolygon method is used. The strip adjustment is performed in such 
a way that the deformed strip surface is forced to fulfil the condition equations for 
scale, azimuth, lateral and longitudinal tilt at the end of the strip. These condition equa- 
tions are obtained from the independent geodetic controls at the end of the strip. This 
procedure yields coordinates for the triangulation points in a local rectangular coordinate 
system which is oriented toward North. To obtain sea level elevations for the triangulated 
points one absolute sea level elevation must be given preferably in the middle of the 
strip. The essential advantage of the method with independent geodetic controls is the 
fact that no geodetie connection is needed beween the measured controls at both ends of 
the strip. This might prove to be a great advantage in areas without geodetic triangu- 
lation or in areas with difficult access such as in jungle or tundras, ete. It is obvious