avoid this problem by basing the greater part of his presentation on his own expe 
rience and research. This approach might appear subjective, or even biased, but 
it helps us to arrive at better founded statements. 
The article begins by discussing the role of information systems in cartography. 
Then the various aspects of the dialogue between a photogrammetric plotter and 
an information system are presented and the prospects for automatic image 
processing are analyzed. By summarizing all these new requirements and possi 
bilities, one can sketch a large range of measuring tools for aerial photographs, 
of which the analytical plotter represents only one of several other possibilities. 
2 . The role of information systems 
The introduction of information systems and the management of cartographic 
information in databases may be considered as a revolution in cartography. It is 
important to realize that the introduction of information systems is not limited to 
the creation of digital plotting systems; an information system must be regarded 
as a central system for storing and managing the information, including graphi 
cal presentations. Generally, the main functions of an information system cover 
the following features : 
data acquisition 
data management 
data analysis 
presentation of the information 
The management of geometric data in an information system requires an appro 
priate structure. One of the characteristics of an information system is that the 
information is structured and in general object-orientated, and that neighbour 
hood relations can be described. These relations are usually established by a 
relational database. This is characteristic of a geographic information system, 
distinguishing it from a simple plotting system. 
For an outsider, the requirement of an object-orientated structuring of the data 
may appear useful, but not necessarily compulsory. However, one has to realize 
that a map sheet contains an enormous mass of data which not only has to be 
stored but also edited and analyzed. A large-scale map easily contains up to 
100.000 vectors, whereas much more can be obtained for smaller scale maps. If a 
house or a part of a street has to be erased, it is often necessary to retrieve the 
coordinates of more than 1.000 points, to change their code or to eliminate them 
from the database. It is only when an object or a part of it can be addressed as a 
whole that one can obtain the necessary flexibility to perform these operations in 
an efficient way and that one can realize the superiority of an information system 
as compared to an automated plotting system. 
A typical working station of a geographic information system consists of a moni 
tor and a digitizer. During data acquisition or data editing, the operator checks 
its activities on the monitor. The same efficiency can be achieved by photogram 
metric data acquisition, provided that the image displayed on the monitor of the 
geographic information system can be injected into the oculars of the plotter, as 
in the Wild System 9-AP. However, one condition for efficient work is that the 
speed of the plotting activity not be affected by the feedback from the geographic 
information system. Nevertheless, due to the complexity of relational databases, 
it is difficult to meet this requirement.