BALLISTIC PHOTOGRAMMETRY, AUTHOR’S PRESENTATION 49
Author’s Presentation of the Paper
The potential of Ballistic Photogrammetry
has developed in accordance with the technical
progress in the fields of rocketry and space
probes. It originated with a subject — probably
not too popular here in London — namely the
development of the V-2 Rocket. Thus, about
1940, the need arose quite suddenly for deter-
mining a sequence of spatial positions for
rather fast moving objects over distances of
100 km or more, with an accuracy comparable
to that of first order geodetic triangulations.
Needless to say, this objective has never been
entirely accomplished. Consequently, the need
for improvement in measuring methods was
carried forward and still today corresponding
activities characterize a major portion of the
total effort in this field of application.
When this work was begun, only tracking
instruments were available for measuring
azimuth and elevation angles. The correspond-
ing measuring procedures are in principle quite
similar to geodetic methods. The photogram-
metric aspect enters here only insofar as the
target is not recorded on the photograph at the
aiming axis of the instrument, but is displaced
due to unavoidable tracking errors. Consequ-
ently, parallactic angular corrections must be
computed from the image coordinates meas-
ured with respect to a simultaneously recorded
fiducial marks system.
The drawback of these instruments is in
the measuring method. Due to the motion of
the target, it is not possible to observe in two
telescope positions and consequently, the
systematic errors of the axes of these instru-
ments cannot be eliminated, which is especially
serious because of the dynamic nature of the
tracking operation. No doubt with ingenuity
and dedication, calibration methods can be
used, for example by photographing arrays of
known auxiliary target boards, but due to the
lack of reference points in the neighborhood of
the actual target, which appears at a wide range
of elevation angles, no satisfactory solution for
determining elevation angles with high ac-
curacy could be devised.
I do not want with this statement to mini-
mize the importance of these instruments, as
they are manufactured by Askania and Con-
traves, for range application where the desired
accuracy requirements are somewhat relaxed,
lets say to 1:10,000 to 1:20,000. An at-
tractive property of these instruments is their
easy adaptability to day time operation.
The family of tracking telescopes with large
focal lengths is a development growing directly
out of the just mentioned cinetheodolite type
instruments. These instruments too, are mostly
equipped with azimuth and elevation angle
measuring devices. Conventional circle read-
ings, as well as, electronic pick-up devices are
used. The principle difficulties in measuring
directions are the same as with the aforemen-
tioned tracking instruments. However, the
extremely long focal length of their optical
systems — mostly mirror optics of Newtonion
and Cassagrainian design, with correction
plates, provide means for securing detailed in-
formation, so-called event photography and
furthermore allowing highly precise photo-
grammetric measurements for problems con-
cerned with the determination of the neigh-
borhood condition of multiple targets, for
instance, by measuring the mis-distance vector
in anti-aircraft firings.
Finally, we come to the actual photogram-
metric type instrument used at the missile
ranges, the so-called Ballistic Camera. Such an
instrument could be described as a glorified
version of a photo-theodolite. Both Zeiss and
Askania produced during the last war such
instruments, especially the Askania photo-
theodolite could very well be considered as a
potential forerunner of today's version, the
Wild BC-4.
The guiding thought in the development of
the BC-4 was to create a phototheodolite of
maximum precision and universal applicability
which could still be classified as a field in-
strument insofar as its overall dimensions and
manuverability are concerned, in contrast to
stationary observatory equipment.
The problem of development of an instru-
ment suitable for ballistic problems is as much
an electronic problem as it is an optical —
mechanical one. The synchronization of the
rotating shutters needed to chop the trail of a
continuous light source must be synchronized
over base line distances of at least 1000 km,
with a minimum accuracy of 1/10,000 sec.
Provided the time jitter in the communication
link is sufficiently under control, a system with
a capability of synchronizing the shutter discs
on the BC-4 to + 25 micro-seconds, has been
developed and is now being commercially
manufactured. A report on the system is avail-
