102 AERIAL TRIANGULATION WITH AUXILIARY DATA, DISCUSSION 
aeropolygon method. Further studies and devel- 
opments of the method, therefore, seem to be 
recommended. Such studies should also include 
the economical aspect of this method. 
d. Another method to be considered here is 
the method with auxiliary oblique photographs. 
This method was essentially developed in Ca- 
nada, by the National Research Council. When 
this method is used 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 photo- 
graphs of the strip triangulations. This proce- 
dure yields auxiliary data for the drift and the 
swing, and they can be used as conditions for 
the strip adjustment especially with respect to 
the y-adjustment. The accuracy of the proce- 
dure depends on the length of the straight lines 
which are transferred from the oblique photo- 
graphs to the vertical photographs. It seems to 
be recommended to acquire more experience 
with this method and to gain more accuracy 
information. 
e. Furthermore, we have to consider the 
Shoran-controlled air stations in connection 
with aerial triangulation. The planimetric co- 
ordinates 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 produced for the air base 
components bx and by. The accuracy of aerial 
triangulation with Shoran-controlled air stations 
may be shown to depend on the accuracy with 
which the air stations are determined by Shoran. 
At present, standard errors of about five to ten 
metres can be expected. A particular aspect 
which should be investigated more thoroughly is 
the economical aspect of this method. 
f. As far as aerial triangulation with horizon 
pictures, sun periscope and gyroscopic record- 
ings is concerned, there is not very much new. 
We know the periscope method, we know the 
horizon picture method, and the only thing that 
is new really is the gyroscopic recording. We 
do not know if this method will reach the neces- 
sary accuracy which we need in precise aerial 
triangulation. 
g. A further method of using auxiliary data 
would be the method with independent geodetic 
control, which actually does not use auxiliary 
data in the strict sense of the word — auxiliary 
data that is airborne data. 
Finally, there are some other methods which 
deal with auxiliary data: Stellar photography, 
Doppler tracking, and Inertial guidance. Then 
there is the dual aircraft mapping system, and 
what is also important here and interesting is 
the study of stabilised mounts for aerial cameras. 
Discussion 
Prof W. SCHERMERHORN: I have heard from 
Professor McNair that he and Professor Doyle 
have something in common. 
Prof F. J. DovLE: I want to say a few words 
about the use of auxiliary data in analytical trian- 
gulation. There are two possibilities for em- 
ploying this kind of data in analytical extension 
which utilizes a simultaneous solution of a large 
number of photographs. In the first method, one 
assumes the positions and the orientations of 
the exposure stations are known, as given by the 
auxiliary control system. Coupled with the ma- 
trix of these positions and orientations is a 
weight matrix for the positions and orientations, 
and this weight matrix is based upon the tested 
accuracy of the auxiliary data. The solution 
then is for corrections to these assumed positi- 
ons. The second form of utilising auxiliary data 
in a simultaneous solution depends upon a pre- 
liminary investigation to determine the function 
which describes the errors of the auxiliary con- 
trol system. In the solution, then, the unknowns 
defining the exposure stations are replaced by 
the parameters of the error equation of the auxi- 
liary system. For example, consider photographs 
made from an orbiting vehicle in which the time 
of each photograph is recorded. Precise vehicle 
position can be expressed as a function of time 
and in terms of orbital parameters. Thus, for a 
strip of, say, 100 photographs the 300 unknowns 
defining the exposure station co-ordinates can 
be replaced by only the six unknowns describ- 
ing the orbital parameters. 
Prof W. SCHERMERHORN: Thank you very 
much for the highly valuable information about 
a new aspect of the use of auxiliary data. 
Prof L. SOLAINI: I speak on behalf of Mr 
Inghilleri. 
We wish to give some information, additional 
to that contained in Dr Brandenberger's report, 
of the work carried out by the Institute of Geo- 
desy and Photogrammetry in Milan. I should 
like to speak especially on the introduction of 
auxiliary data in analytical triangulation. 
The analytical proceedings in respect of the 
  
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