The Planimat, a new second-order photogrammetric plotter 
by Dr.-Ing. M. AHREND, Oberkochen 
If we follow the usual classification of photogrammetric plotters and leave aside further details 
regarding operating principle, application or accuracy, which would normally be required to describe 
such complex equipment, we find the following categories: 
First order: Universal instruments (precision plotters of great versatility) 
Second order: Precise instruments (precision plotters for mapping and numerical plotting of indi- 
vidual models) 
Third order: Topographic instruments (medium and small-scale plotters). 
Messrs. Carl Zeiss of Oberkochen have now added the ‘‘Planimat” to their line of equipment, 
which belongs to the second-order group mentioned above. In the following, the Planimat and some 
of its special features will be described in further detail. 
1. Requirements 
In the design of a plotting instrument, allowance must be made above all for the following factors: 
1. its field of application 
2. its cost 
3. its accuracy, and 
4. its economic use. 
In this connection, the Planimat was to satisfy the following requirements: 
A precise photogrammetric plotting machine was to be created which would combine the simplest 
possible design with the most important practical photogrammetric stereoplotting capabilities. By 
comparison with the universal C-8 Stereoplanigraph plotter, it was here specified that: 
g and o tilt ranges were to be limited to about 5? instead of 30? and 60^, respectively. The focal- 
length range should be as large as possible. Plotting with small bx-base values should be feasible. The 
cost of the instrument should be about half that of the Stereoplanigraph, which might impose certain 
restrictions regarding ortho-pseudo change-over, base-out setting and the z and y-ranges. The drawing 
operation proper should not only be performed on an external tracing table connected to the instru- 
ment, but also right in front of the operator's eyes. The accuracy of the instrument should be iden- 
tical with existing precision plotters, i. e. the mean square coordinate error in the image plane should 
be less than + 10m, and the relative mean square vertical error should be less than 4- 0.1 9/99. To 
increase the economy of the instrument, it should be suited for plotting both normal-angle and wide- 
angle as well as ultra wide-angle photography. 
2. Design principle 
Fig. 1 shows the design principle of the projection system used in the Planimat. Two mechanical 
guide rods La, Lp connect the space point G, the perspective center P and the image-plane reference 
point D. 
The space points G can be shifted in relation to each other to allow the base bx to be introduced; 
in addition, the space point G4 can be displaced for the introduction of bz, the space point Gs for the 
introduction of by. The space points Ga and Gg are jointly moved in z, x and y. For the introduction 
of the calibrated focal length f, the perspective centers P are displaced vertically. The vertical di- 
stances PD = f and PG = z thus represent the usual projection distances. We may therefore describe 
the projection system as a design using ‘single-arm mechanical, spatial guide rods and two space 
points", in which the guide rods are supported by the space points G. 
A brief review of other mechanical projection systems using straight guide rods may serve to 
illustrate the disposition chosen for the Planimat: Figs. 2a to 2g show the possibilities of arranging an 
individual guide rod, while Figs. 2h and 2i illustrate its use during stereoplotting. As is evident, 2 d 
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