23 
e). Plotting device. 
The drawing surface (600 x 800 mm) is located on top of the projection (model) computer 
in front of the operator. It is provided with an orthogonal coordinatograph. The trans 
mission ratio from model to map can be changed between 2:5 and 1:1 in several steps 
by changing the gears. 
IV. NEW ACCESORIES AND IMPROVEMENTS OF EXISTING MECHANICAL RESTITUTION 
INSTRUMENTS 
IV. 1 Kern PG2. 
Without changing the construction of the instruments, a few accessories have been developed 
which facilitate some extensions of its application. They concern: 
a) , increased range of plotting scales. 
b) . numerical restitution, 
c) . possibility for aerial triangulation. 
d) . optical correction plates for lens distortion and special grid plates for metric tests. 
a) . Range of plotting scales. 
For plotting, three devices can be used: the L-pantograph for enlargements (model to 
map) between 1:1 and 1:3. 333, the R-pantograph for reductions (with pole outside) 
between 1:1 and 2:1 and enlargements up to 1:1. 8 (with pole outside), and an arm, 
rigidly attached to the parallel guidance, for plotting directly in model scale. The 
position of this arm is adjustable. 
b) . Numerical restitution. 
Fig. 16 shows the principle of the determination of planimetric coordinates of model points 
by angular measurements. 
Fig. 16. Determination of planimetric coordinates.