98 AERIAL TRIANGULATION WITH AUXILIARY DATA, BRANDENBERGER 
different reliability. It has to be pointed out, however, that under normal conditions a 
remarkably high accuracy for the air station altitudes can be obtained from statoscope 
data. According to experiences in Finland and Switzerland the standard errors for sta- 
toscope air station altitudes amount to one to two meters. Altimeters normally yield a 
lower accuracy because most of these instruments are less sensitive than statoscopes. 
Since the errors of statoscope air station altitudes affect the elevation accuracy of 
aerial triangulations performed by means of such auxiliary data it is desirable to reduce 
the effect of statoscope errors. Such a possibility exists by determining these errors from 
the Am-rotation of the fixed camera in case that a strip triangulation is performed in a 
first order stereo plotting instrument according to the principle of aerolevelling. The ac- 
curacy of this procedure depends on the accuracy of the Ag-rotations which in turn is 
depending on the accuracy of the relative orientation performed with both @-rotations. 
The accuracy in determining the errors of statoscope air station altitudes from the Ag- 
rotations of the fixed camera furthermore depends on the flying height above ground of 
the aerial triangulation in question. It seems to be, however, that only for low flown 
aerial triangulations the method using the /g-rotations is sufficiently accurate to deter- 
mine statoscope errors while for high flown aerial triangulations, say above 6000 m 
flying height above ground, the statoscope air station altitudes might be very probably 
more accurate than the air station altitudes determined from the 4g-rotations of the 
fixed camera. 
b. The bz — 0 method. 
Although this method of strip triangulation does not use auxiliary data in a strict 
sense the procedure is very similar to the strip triangulation procedure with statoscope 
data i.e. the aerolevelling procedure. For this reason it is felt necessary to include this 
method in this report. When a strip triangulation according to the bz — 0 method in a 
first order stereoplotting instrument is performed it is assumed that all stations have the 
same altitude i.e. both bz in the instrument are left on zero and the relative orientation 
is carried out by means of both ¢ instead of bz. Since the above mentioned assumption 
is not normally fulfilled considerably 4g-rotations of the fixed camera occur. The real 
air station altitudes are then computed from these 4g-rotations in a similar way as the 
statoscope errors are determined [see section a.]. With regard to the attainable accuracy 
for the air station altitudes determined in this way the same considerations hold as in- 
dicated in section a. 
€. The radar profile method. 
Experience has shown that by means of this method a high accuracy can be obtained 
for relative heights from the air stations to ground points on the profile path. This ac- 
curacy seems to be higher than that which is obtained for the relative heights from an 
aeropolygon strip triangulation performed in a first order stereoplotting instrument. 
There is no doubt that sufficiently accurate distances from air stations to profile points 
Which are measured by the radar profile recorder represent very valuable auxiliary data 
which can greatly contribute to stabilize strip triangulations and to reduce the excessive 
error propagation of the aeropolygon method. Further studies and developments of this 
method therefore seem to be recommended. Such studies should also include the econom- 
ical aspect of this method. 
d. The method with auxiliary oblique photographs. 
This method was essentially developed in Canada [National Research Council]. When 
this method is used greatly oblique photographs with an auxiliary camera are made in 
addition to the regular vertical photographs. From the oblique photographs straight lines 
in flight direction are transferred to the individual vertical photographs of the strip 
—rr teet