PHOTOGRAMMETRIC ENGINEERING
Fıc. 6. The arrangement of two pictures for stereoscopic measurements of the deformations.
mine deformations of a ship and simul-
taneously the shape and size of the waves
along side the ship.
During the trip to the International
Congress of Photogrammetry in Washing-
ton, D. C., 1952, a phototheodolite and a
number of stereocameras with bases of 120
and 40 cm., were used for the experiments.
The experiments were performed primarily
to get experience prior to later investiga-
tions; of course the ship, a stable passenger-
ship, was not expected to undergo any
large deformations. Dr. P. O. Fagerholm
took part in the experiments and used
some of the instruments on his return to
Europe on a French ship. The author used
the rest of the instruments during his re-
turn on a Swedish ship. All these experi-
ments, however, suffered from the natural
perversity of the elements. During both
trips there was the most perfect tourist
weather. Bad weather would have made
the experiments more interesting and such
weather was expected as some of the voy-
ages occurred during the autumn, a season
which generally brings the bad weather.
No deformation of the ship could be ob-
served but important experience was ac-
quired for later experiments on tankers or
ore-loaded ships, which are much more
sensitive to rough seas.
The following are some details concern-
ing the measurements and computations.
For determining the deformations under
these circumstances the influence of the
outer orientation changes of the camera
upon the image coordinates must also be
taken into account. In other words, the
camera itself is mounted in a point which
also takes part in the deformation move-
ments, and the distances dz' (Figure 1) can
be caused by the movements as well of the
features points as of the camera station.
If limited to the determination of the de-
formations in a plane through the camera
axis and the vertical fiducial marks, par-
ticularly the influence of a rotation dw of
the camera around an axis through the
perspective center and normal to the men-
tioned plane must be considered.
The influence upon the images coordi-
nates z/ of such a rotation do is given by
the wellknown formula:
da! = (1 +) do (2)
! See for instance V. Gruber: Photogram-
metry. American Photographic Publishing Com-
pany. Boston. 1942.
