For operations at lower altitudes light twin-engine aircraft,
which use much less fuel per hour, are most economical. Heli-
copters such as Wasp and Whirlwind have been fitted with F9
MK2 wide angle survey cameras and Bell 47 IT with Wild Re 8.
However, after U0 years of invaluable service, the workhorse
ofsthecair, the CU7 or Dakota DC3, 18 far from dead. Probably,
about, 2/000 of DC3 craft are still flying. Quite a few are
used in aerial photography for overseas operations and geo-
physical prospecting missions.
"roblems on survey navigation and integration of flight sys-
tems have been studied in an invited paper by Corten,: ITC (17).
The report deals with self-contained navigation systems in ge-
neral, and gives two specific examples, one of a doppler-inte-
grated system, and another one of an inertial-integrated system.
Experiences of Doppler navigation and multispectral photography
are reported from Mexico (13, 14). The new automated ITC Phot-
nav System, its economy and the benefit which can be derived
from it, has been described (20, 21). The particular problems
Of flight planning for ortho photo mapping have been studied
by Hobbie (56) and Schóler (59). Owing to the strong connection
between the location of the Plight strips and the map sheet di-
vision in ortho mapping, a high accuracy of the survey naviga-
tion and at least 80% forward overlap facilitates the mapping
procedure. An Italian report shows how the flight planning is
donenfor 1:5 000 andcı:20 000 schle mapping in mountain areas
(55.
Since several years, the big camera manufacturers provide re-
liable navigation sights. However, the old "side sighting" me-
thod is still in use. When flying, ground features through
which the side sight passes, are memorized or sketched onto a
roll of paper. On the reciprocal run, the aircraft is naviga-
ted so that the side sight is made to pass through the same
ground features. Fairey Surveys (7!) has incorporated this
simple principle into a nicely engineered drift setting and
levelling Photo Navigation Sight, which has the distinct advan-
tage of being useable in areas, where no maps or inadequate
maps are available.
An equipment for automatie exposure control has been described
by Lorch (43). A sensor whose sensitivity is limited t6-the
Spectral range of panchromatic film is used. The aperture and
shutter speed are controlled by servo-motors. The film speed,
the filter factor, and admissible image motions between 10-40 um
can be set. However, the use of an automatic exposure control
does not make the experience of a qualified operator obsolete.
Just on the contrary: only an experienced operator having a suf-
ficient background of the equipment and the photographic mate-
rial employed will be able to make full use of the advantages of
automatic exposure control.Moreover, he will recognize situa-
tions off the beaten track in which he himself should take com-
mand. Properly used, an automated eXposure control system will
help an experienced operator obtain more uniform image quality
and eliminate exposure errors.
