i8o
instrument may eventually also be used as a co-ordinate reader,
with automatic recording of co-ordinates. A detailed description is
given by C. Trombetti in [103].
The Cartimat made by Optical Works Jena is available in several
models. The simplest type allows only automatic point-plotting
and automatic recording of co-ordinates of set points. A somewhat
more versatile model also allows the drawing of straight lines
and curves. It is possible to couple this table to a special calculating
unit for scale alteration, co-ordinate transformation etc. A descrip
tion of the Cartimat system can be found in [104].
The Cartimat's effective size is 90 x 120 cm. The highest drawing
speed is 2.5 cm/sec. The manufacturer gives approx. 0.05 mm as the
plotting accuracy.
The Auto-Trol Corporation makes, among others, a high speed
automatic co-ordinate plotting and drafting machine, model 6000.
The drawing area of this is 125 X 180 cm. It is possible to draw at
four different speeds, varying from 10 to 75 cm/sec. The maker
states a drawing accuracy of abt. 0.1 mm. The question is for what
period an instrument capable of drawing 400 lines of 2.5 cm length
per minute, can maintain this accuracy.
Dennert Pape of Hamburg specializes in automatic drawing
tables of very large size. These drawing machines are very robustly
constructed. The table with a drawing area of 200 X 260 cm,
weighs about 1 100 kgs and requires over 4x5 metres of space,
excluding the control unit. The manufacturer gives a drawing
accuracy of about 0.15 mm at a speed of 2 cm/sec. The smaller
sizes are designed to be used in geodesy and road design. The
larger formats are more in demand by the ship building and air
craft industries, etc. The largest size made by this firm up to now,
has a useful area of 3 x 10 metres.
Dennert Pape also manufacture instruments for co-ordinate
recording specially for the metallurgical industry. Here again, large
sizes are used which would hardly be of interest for survey work.
Better tailored to the needs of surveyors is the product of Coradi
(Switzerland), the automatic drawing table called the Coradomat.
Besides making drawings, the Coradomat can also be used for
recording co-ordinates of set points. This is done rapidly and
accurately by means of an episcopic projection system giving a
magnified image of a part of the drawing to be measured on a
frosted screen. The draughting area is 130 X 160 cm. At a drawing
speed of about 5 cm/sec. an accuracy of about 0.05 mm is attain
able, according to the manufacturer.
The Kongsberg Vbpenfabrikk in Norway markets two electronic
drawing tables, of which the smaller one, with a drawing area of
120 x 150 cm, is the most suitable for survey work. According to
information supplied by the manufacturer, a drawing accuracy of
about 0.1 mm is attainable when operating at a speed of about
15 cm/sec. The larger size, 260 X 370 cm, is basically designed for
