> geometrical relations (e.g. is_parallel_to)
In our data model it is possible to deter-
mine whether two spatial objects are paral-
lel (vertical) or not. Those objects with an
area as geometry the diameter [Preparata &
Shamos 1988] of the area is determined and
used for the calculation. Also we can calculate
the distance between objects.
e operators for aggregation of spatial objects
(e.g. convez hull, closest object pair, ..)
To create new generalized or grouped objects
we have implemented a convex hull algorithm
[Preparata & Shamos 1988] for different kinds of ge-
ometry classes (Point, Line, Area). Also we have
implemented methods to determine the nearest ob-
jects to a given object. This problem can be solved
by the Voronoi Diagram [Preparata & Shamos 1988]
in the case of points. For lines and areas we use a
centroid point.
| | |
Topology Structure OverUnder Neighbourhood
disjoint(A,B is_part_of(A) : Set is_over(A) : Set distance_to(A,B)
Soins. ) has parts(A) : Set is under A n lies. beside(A) : Set
overlap(A,B) insert, part(A, B) = : ghbourhood_of(A)
covers(A,B)
coverd_by(A,B)
inside(A,B)
contains(A,B)
equal(A,B)
Figure 10: Class of object relations
6 CONCLUSION
Because of the increasing amount of spatial information in
digital form and the importance of data actuality and data
quality for economy, industry and commerce it will become
more and more important to automize the revision of dig-
ital landscape models. Within this article we described
an approach for data mining in spatial databases to de-
duce implicit given information. Also a knowledge based
shell for an object oriented spatial database was designed.
We described some examples of possible applications in
the area of automatic data revision. The automatic in-
terpretation of digital landscape models is a new field of
interest for GIS research and far from being solved. For
the time being we are only able to detect low level ob-
ject information like geometrical or topological relations
(based on the given object geometry) and we have some
aggregation operators to create new objects developed. In
the future work the frame based knowledge representation
has to be developed to control the interpretation process
and to deduce high level object information.
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