a digital terrain model, Soviet photogramme-
trists have developed a system that includes a
stereoplotter with digital readout, an electronic
computer, and a phototelegraphic plotter (Zap-
tsev, Laurova, and Chigirev, 1978).
The stereoplotter provides the input infor-
mation for the digital computer, derived by
scanning the model along different trajectories.
The computer transforms the collected data
into an energy spectrum at intervals x and y of
a rectangular coordinate grid. Light pulses fed
from the computer to the phototelegraphic ap-
paratus generate a digital relief model at the
grid intersection points.
The input unit is a Drobyshev SD-1 Stereo-
graph equipped for connection to the digital
computer by means of digital encoders ; a pro-
graming unit provides stepped drives for mo-
ving the base carriage in the x, y plane.
The Dnepr-1 controlling electronic compu-
ter performs the following functions : Determi-
nes the limiting frequencies of relief spectrums
for different directions ; computes the x and y
steps of the rectangular grid ; computes the ele-
vations of intermediate points of the digital mo-
del ; determines the applicability of each point
to a contour line ; outputs points on contour
lines in the forme of pulses with amplitude pro-
portional to the weight of the contour; and
controls movement of the curve plotter apertu-
re synchronously with an analysis of the compu-
ter elevations of points.
The output unit is a phototelegraphic appa-
ratus (PTA) Neva equipped with stepped dri-
ves along the x and y axes. Light pulses fed
from the digital computer to the PTA are am-
plified to modulate the light flux of the gas
lamp in the optical head. Either a positive or a
negative image of the contour lines can be ob-
tained.
SWITZERLAND
Developments in Switzerland pertain mainly
to modernization of instruments manufactured
there and to investigation of applications of
those instruments to automated systems.
Profile scanning with stereoplotter and electro-
nic readout
A system for profile scanning with the Kern
PG 2 plotter (Klaver, 1973) has been develo-
ped. The system (PS-2) consists of a cross-slide
that guides the tracing stand through a hookup
to the pantograph. The PG 2 operator can mo-
ve the tracing stand only in the direction of
the cross-section so that he does not have to
look away from the stereomodel while he scans
the profile and records the coordinates of all
required points. Recording is by means of an
electronic model-coordinate readout system,
Stereopplotter with automatic plotting table
The Kern PG 2AT semiautomatic stereo-
plotter system (Klaver, 1975) is composed of a
PG 2 with x, y, z encoders and an automatic
plotting table linked by electronic interface
with electronic scalers. Scale factors are 0.7 —
9.9, giving a maximum enlargement of 12.5X
from photo to plot. The automatic modes are
controlled by a hard-wired microprocessor. The
automatic coordinatograph can also be used off-
line.
System for orthophoto production
A new, universal orthophoto system develo-
ped by Wild Heerbrugg (Stewardson, 1974) is
designed to provide a fast, flexible, and accu-
rate transformation of a perspective to an or-
thophoto. It operates on-line or offline; ac-
cepts any focal lenght ; accepts either positive
or negative imagery ; accepts either black-and-
white or color photographs ; corrects for linear
transverse slope ; has variable scan speed ; and
operates in normal room lighting. The model
currently being built and tested is called Avio-
plan OR-1. The system probably will be fully
developed and available by the time of the Hel-
sinki Congress.
UNITED KINGDOM
Although a significant United Kingdom ef-
fort in automated cartography has been moun-
ted, the progress in automation of photogram-
metry has been relatively modest.
Stereoplotter-computer combinations
Two British commercial firms have establis-
hed on-line systems for producing digital ter-
rain data from photogrammetric models. Hun-
ting Surveys has connected some 10 Wild AS's
to a large PDP computer, and Topographic In-
ternational has a Zeiss Stereometrograph on-
