Hempenius, Makaroviè, Van der Weele, Tests of Restitution Instruments 
i 
function : 
For the constant K = 
e 
~Al 
F (d) =Kv (d) 
can be taken : K = l 
(13a) 
The function v (d) has to be 
determined experimentally. 
Various plotting instruments should meet the requirements for which they were in 
tended. Most critical, however, is the performance of the smallest symbol d to be reliably 
reproduced. This critical size d of the symbol could be standarised for different types of 
plotters or various map scales. The condition is that d > d min , where d min is the smallest 
size of symbol (circle) which still can be performed. 
If the symbols are the sinusoidal* curves, the conversion into corresponding frequency 
spectrum v i is according. 
1000 [pm] 
Vi 2 d i [pm] 
Subsequently the relation (13a) may be written as: 
F,(v) =Kv (v) (13b) 
This criterion is not fully satisfactory, because it does not specify the quality of the 
performance. Therefore the transfer function defined as: 
4 a (r) • v 
1 — 
103 
= Q (v), 
(14) 
represents the significant supplementary information (fig. 10). A useful addition to the 
speed function F (v) and transfer function q (v) may represent the combination (fig. 11): 
_ F(v) 
<P ( v ) 
o (V) 
(15) 
in which both essential components are contained. 
§ 
13 
Fig. 10. The information transfer function. 
Fig. 11. The combined criterion. 
When the investigation is restricted to the critical frequency range only, the above 
functions are replaced by appropriate values F, ft and <P — F/d, which correspond with the 
standarised smallest size d of the representative symbol. 
III. 7. Representation of disturbances. 
In the example discussed the two characteristic groups (t, t, T) and (A, l, L) are 
separated according to their consequences in the output, while the separation within each