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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