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AERIAL TRIANGULATION WITH AUXILIARY DATA, BRANDENBERGER 97 
aerial photography, considerable efforts have to be made to increase the inherent ac- 
curacy of auxiliary data. 
If the various procedures of aerial triangulation with auxiliary data are studied and 
compared it is found that especially one problem needs to be more cleared up, namely 
whether auxiliary data should be directly introduced in à first order stereo plorting in- 
strument during the strip triangulation or whether such auxiliary data should be only 
used for the adjustment of strips triangulated according to the aeropolygon method. The 
same problem also occurs when analytical strip triangulation with auxiliary data is con- 
sidered. 
With regard to block triangulation with auxiliary data it is to be pointed out that 
such blocks are composed up to date exclusively from individual strip triangulations. 
This composition is basically the same for both the aeropolygon method and the pro- 
cedures of strip triangulation with auxiliary data. This means that the main efforts are 
to be directed toward improvement of the accuracy of individual strip triangulations 
when one of these two methods should yield a superior accuracy. 
When the efficiency (required time and costs) of aerial triangulation with auxiliary 
data is compared with the aeropolygon method it is to be taken into account that in the 
first case additional equipment and costs are required to produce auxiliary data. On the 
other hand it is to be taken into consideration that aerial triangulation with auxiliary 
data generally requires less given ground control points for the adjustment of strip trian- 
gulations than the aeropolygon method. This is due to the fact that aeropolygon method 
requires the determination of more unknown coefficients in the error propagation for- 
mulas than strip triangulation with auxiliary data. It might be concluded, therefore, that 
strip triangulation with auxiliary data would be more efficient in areas with extremely 
poor geodetic controls when compared with the aeropolygon method. On the other hand 
this method might prove to be more efficient in areas with a rather dense network of 
geodetic controls. 
From the various national reports follows that at present a great variety of auxil- 
iary data are used in carrying out aerial triangulation. This variety is so great that the 
reporter felt it necessary to summarize the status of aerial triangulation with auxiliary 
lata in the various countries separately. For the same reason a comprehensive summary 
of the various systems or methods of producing or using auxiliary data is given below: 
a. Aerial triangulation with statoscope and altimeters. 
Statoscopes, and altimeters yield air station altitudes or air station altitude differ- 
ences. If these data are used in performing a strip triangulation they can be converted 
into bz-values which can be used as fixed bz-values in a first order stereo plotting in- 
strument [aerolevelling method] or as additional information for the adjustment of a 
strip triangulation performed by the aeropolygon method. When statoscope or altimeter 
data are used one has to keep in mind that the accuracy of such information depends on 
the inherent accuracy of the instruments being used and the anomalies of the isobaric 
surfaces. The instrumental accuracy of statoscopes and altimeters can be determined by 
appropriate tests while the anomalies of the isobaric surfaces and their influence upon 
air station altitudes can be determined only from additional meteorological information. 
If such additional information is to be used a sufficiently dense network of meteorolog- 
ical stations must be available. This requirement might be considered as an inconvenience 
since in many areas on the earth there are no meteorological stations available or there is 
no possibility of obtaining meteorological data to correct for anomalies of the isobaric 
surfaces. 
The anomalies of the isobaric surfaces depend on the local atmospheric conditions 
which are more or less different from country to country. This means that in various 
areas or countries air station altitudes determined from statoscopes or altimeters are of