172
♦
used, the image pairs can be plotted directly or transformed for a
focal length which can be set on the Autograph.
The ideal plotter for terrestrial photogrammetry is the Wild Avio-
map AM U with the new Aviotab TA Plotting Table. Aerial and terres
trial photographs up to 23 cm x 23 cm can be plotted. The focal
length range is 54 mm - 311 mm. A remarkable feature of this instru
ment is that it can plot from tilted photographs for every angle
from 0 to 100 u by means of a tilt calculator or azimuth control.
The plotting table Aviotab TA, which can be attached to the Aviomap
AM U, tilts from the horizontal to an almost vertical position.
Furthermore, there is a hydraulic control for raising the entire
table. The operator remains in close contact with his manuscript
and can effortlessly enter corrections and addenda on the plotting
sheet.
The costs and efficiency of terrestrial photogrammetry
The application of close-range photogrammetry in architecture, con
servation of monuments, archaeology, industry and research has de
veloped into a time-saving and efficient method of measurement.
In spite of the varied nature of the problems involved, the univer
sality of the photographic and plotting systems ensures great economy.
Production instruments were first used in the early 1930's when Swiss
traffic police gradually acquired equipment for photogrammetric gathe
ring of evidence. The newly developed equipment consisted of the C 12
Stereometric Camera and the A 4 Autograph and is still used today in
some places for photogrammetric evaluation of accidents. Several
decades of experience were behind the development, in the early 1960's,
at Wild Heerbrugg of a new photographic and plotting system: The Wild
C 120 Stereometric Camera and the Wild A 40 Autograph described above.
These instruments capture and reconstruct the scene of an accident or
other evidence, thus shortening and simplifying, in comparison to
other methods, the work involved and making a material saving of per
sonnel , time and money possible.
A telling argument in favour of photogrammetry is the small
amount of time needed to gather the evidence at the scene of
the crime or accident. Reports have indicated that a saving
in time of more than 50 % can be achieved by using photogram
metric rather than conventional methods.
The following example illustrates the time involved in pro
ducing a photogrammetric evaluation of a medium-sized accident:
Securing and marking the marks of the accident
0.1
h
( 2
%)
Preparing and making 6 stereo pairs
0.3
h
( 6
*)
Photo lab work (development)
0.5
h
(10
%)
Making copies and enlargements
0.8
h
(16
%)
Photogrammetric plot of 6 stereo pairs
1.5
h
(30
%)
Fair copy of the drawing and creation of
the accident file
1.8 h (36 %)
