582 
Boehler, Emmel 
Figure 2: Time reference, geometrical dimension and Figure 3: Rhine Valley near Kaub. (Virtual landscape 
abstraction level define different aspects of a GIS based on a DEM and a LANDSAT TM image) 
Extent of Abstraction. An information system can only contain a model of the real world. Therefore, rules for the necessary 
abstraction process have to be defined before the database is created. 
If topographic features are documented merely by texts, only a limited perception can be obtained by the reader. This is why maps 
are used. They also have a high level of abstraction, since small geometric features are omitted, reducing the real-world features to 
symbols and colors which are explained by short texts inside the map frame or in a legend. The advantage of this approach is the 
option to show features that are too small to be visible (such as a small monument) or even invisible (such as the classification of a 
road) on a photo-realistic view. A GIS database uses the same abstraction techniques but can include much more information since it 
does not have the restriction of a map where only a certain amount of information can be shown in the available map sheet area. 
Photo-realistic landscape representations can be obtained as aerial photographs or satellite imagery. Obviously, they have a different 
and less abstract nature as compared to maps. Semi-realistic presentations can be achieved if map features (symbols, transparent 
colors) are combined with digital image information. 
A GIS can contain and link information of any level of abstraction and offers the possibility of presenting any selection or 
combination of data in textual or graphical form. 
Multi-temporal systems. A landscape represents not a state but a continuous process. Therefore multi-temporal GISs are desirable 
because they store and present past and future situations and developments over time. 
If the geological development is to be modeled, changes to the DEM caused by uprising, eruptions, sedimentation or erosion are 
required. Software for the modeling of DEM changes has been developed at Bmainz since it is not possible using commercial GIS 
packages (Böhler et al., 1999). 
In landscapes, changes usually materialize in the form of land cover changes due to variations in environmental conditions (mainly 
climate) and human impact (deforestation, agriculture, settlement, infrastructure). GIS producers have not really solved the problem 
of time as a fourth dimension of spatial information. However, if historical situations are included in a GIS as additional layers, a 
satisfactory representation can be achieved. 
Changes occurring in landscapes have to be permanently incorporated into the system to keep it updated. Before the system is set up 
it must be established whether updates will replace current fdes or if all fdes have to be maintained to gradually create a multi 
temporal system. 
Furthermore, future landscape conditions can be simulated and visualized using digital systems. Visualization of alternatives and 
simulations is a valuable tool for planning and decision-making. Time-dependent changes can also be presented as videos. 
5. DIGITAL REPRESENTATIONS OF THE RHINE RIVER VALLEY 
Since UNESCO has suggested the delivery of a model nomination for the Upper Middle Rhine Valley (UNESCO 2001), Bmainz 
proposes solutions which are especially suited to meet the conditions of this area: 
5.1 Basic GIS 
Basic GIS components, ATKIS and ALKIS, are already available from the local surveying authorities. To prepare the UNESCO 
proposal this information has already been converted to ArcView shape fdes. It can be transferred to the Arclnfo format (as 
suggested by UNESCO), thus giving a basis which can be used for any GIS analyses and presentations.