Photogrammetria, XIX, No. 6 
The evaluation of the overall dynamic performance is important for the design, 
manufactoring and maintenance of plotting instruments. 
Dynamic analysis can be based on a theoretical or experimental approach [5]. The 
theoretical analysis is a useful tool in the designing of dynamic systems or their compo 
nents. It is based on the simulating differential equations of the process in which the time 
(or a selected direction) is the independent variable, the input is the known function of this 
direction (forcing function), and the output is the dependent variable. The coefficients in 
differential equations represent the physical parameters of the system (e.g. friction, mass, 
elasticity, etc.). 
The performance is evaluated from the solutions of the differential equations descri 
bing the process. This is often rather cumbersome, especially if the parameters of the 
system are not known. 
The experimental approach is applicable in existing systems or analog models of 
them. The dynamic system is subjected to edequate inputs, and the output is recorded as 
a function of the independent variable (e.g. a selected direction or time). The most common 
standard input is the sinusoidal change. 
The input is a forcing function, given to the system but independent on it. The output, 
however, has undergone the physical characteristics of the system; it is the response 
function. 
Analysis is most efficient when the frequency response method is used in which the 
input (forcing function) is a sine wave. 
The flow of information from its source — the photograph, to the map sheet on the 
drawing table is influenced by several disturbing and limiting effects. Their origines and 
consequences are properties of the plotting system, through which the information flows. 
For the purpose of analysis it is convenient to set up the functional block diagram of the 
plotting apparatus concerned. Then all possible sources of disturbances or limitations 
within the system can be studied. 
The proposed method of analysis [6] is adapted to the fundamental concepts of the 
information theory [8], [7]. Fig. 2 shows a general block diagram of the information 
flow in the communication techniques. 
Fig. 2. Block diagram of the information flow (general) 
The information is transmitted from its source in form of messages, which are resol 
ved into elementary symbols, via the communication channel to the receiver, where they 
are recorded. The messages may be resolved into a finite number of discrete symbols or 
into continuously changing elementary units. These symbols are transmitted in form of 
adequate signals from one physical system to another. 
Due to imperfections in the communication channel the receiving signals suffer some 
losses. After reception they are converted into elementary symbols, with losses, which 
compose the messages and subsequently yield the transmitted information. 
An analogous block diagram for a conventional photogrammetric plotter, with a 
movable optical system, is illustrated in fig. 3. The source of information is the recorded 
image (photograph). From it the desired information (planimetry) is extracted in form 
of cartographically idealised line figures (e.g. roads, buildings, etc.) or parts of them.