ISPRS, Vol.34, Part 2W2, “Dynamic and Multi-Dimensional GIS”, Bangkok, May 23-25, 2001
162
RESEARCH ON INFORMATION AUTOMATIC GENERALIZATION WITH VARYING MAP SCALE
Yuanhui LI 1 Dan LIU 2 Yifan LI 3
1 Nautical Science and Technology Institute
Dalian Maritime University, Dalian, China, 116026
Tel:86-411-4729297
E-mail: yuanhuilee@hotmail.com
2 Nautical Science and Technology Institute
Dalian Maritime University, Dalian, China, 116026
Tel:86-411-4729297
3 Nautical Science and Technology Institute
Dalian Maritime University, Dalian, China, 116026
Tel:86-411-4729297
E-mail: yifanli@163.net
KEY WORDS: Information Automatic Generalization, Varying Map Scale, Topological Relation
ABSTRACT
The change of spatial topological relation and how to recover these topological relations through studying the change of objects’
geometrical relation are studied, twelve approaches have been given to resolve 12 kinds of geometrical deformation in map
generalization.
1. INTRODUCTION
Along with the development of GIS in various application field,
the existing GIS data processing technique can not meet with the
requirements of space times and information society, the
important problem is that GIS can not resolve the increase and
decrease of information when data on vector space change with
scale. Namely, the problem of extraction and recovery of space
information with the varying map scale. The varying map scale
GIS is a kind of information processing techniques for extraction
and recovery of GIS space information in accordance with the
scale, which the information of spatial objects increases or
decreases automatically along with the change of the scale in a
certain region, based on a big database. Varying map scale
technique includes map automatic generalization and information
automatic generalization. Many scientists had made a detail
definition and analysis for map automatic generalization and
gained mature results, But Information automatic generalization
is emerging, which mainly studies the change of spatial objects’
topological relation, geometrical relation and attribute relation in
information extraction of GIS when map automatic generalization.
This paper mainly research into the change of spatial topological
relation and how to recover these topological relations through
studying the change of objects’ geometrical relation.
2. THE CHANGE OF INFORMATION IN MAP AUTOMATIC
GENERALIZATION
As all known, the following means influence the geometrical
relation of map in map automatic generalization:
1. Selection of diagnostic object sign
2. Displacement
3. Distortion
4. Merging
So, we can get 12 kinds of change in map generalization.:
1. Reshape polygon to counter self-coalescence
2. Reshape two polygons to counter coalescence
3. Displace polygon to counter coalescence
4. Select subset of points to counter congestion
5. Amalgamate polygons to counter coalescence and
congestion
6. Partial area collapse to counter self-coalescence
7. Area conversion to counter congestion
8. Typification in sets of polygons to counter congestion
9. Dissolution in a subdivision to counter imperceptibility
and congestion
10. Exaggeration amidst other features
11. Exaggeration in a subdivision
12. Typification of a polygon to counter self-coalescence
3. INFORMATION AUTOMATIC GENERALIZATION WITH
VARYING MAP SCALE
Points are independent objects in topological data structure and
they can be connected each other to form a line. Line is
constituted by a series of connected points, starting with a start
point and ended by a terminal point. String is a line of one or
more polygons, also called arc or edge. Node is the intersectant
point or the terminal point of line or string. A polygon is composed
by a outer ring and zero to more inner rings, and a ring is
composed by one or more strings. This shows that the essential
geometrical structure in topological data is line, so we should
generalize line, then smooth it and process consistency check.
Now we discuss the change of topological data based on 12
kinds of deformation in map generalization.
1. Deformation of single polygon
We only need change the deformation of the line related to
this polygon. A SHAPE polygon q ^ _ ( u v ( 5 )) is given,
make a polygon S*(s, t) through these lines, t is the parameter of
the SHAPE polygon, then s * (s, t) = (U(s, t), V(s, t)) and
U(s,t i ) = u l (s),V(s,t i ) = v i (s)
Vf e [0,1] .make S(s,t)=(x(s,t),y(s,t),z(s,t)),so
S(s, t) = P(t) + a(s, t)x(t) + b(s, t)y(t)
a(s,t)and b(s,t)isdefined as follows:
Let
m x = minU(s,t),m 2 = ma xU(s,t)
m, = min V(s, t),m A = max V(s, t)
sc x
m 2 - w,
sc.,
-m 2
|/ 4 (0-/ 3 (0|
then
