ISPRS, Vol.34, Part 2W2, “Dynamic and Multi-Dimensional GIS”, Bangkok, May 23-25, 2001 
169 
4.3 Thematic information 
The thematic information for the two maps shown in Figure 1 is 
also computed and shown in Table 3. It is very clear that the 
map shown in Figure 1a has more thematic information because 
the tree symbols are scattered around building symbols. On the 
other hand, the thematic information contained by the map 
shown in Figure 1b is lower because the three types of symbols 
are quite clustered. Therefore, the thematic information defined 
in this way seems very meaningful, as well. 
Table 3 Thematic information of the two maps in Figure 1 
Thematic Information H(TM) 
Map in Figure 1 (a) 
28.2 
Map in Figure 1 (b) 
16.4 
5. CONCLUSION 
In this paper, existing quantitative measures for map information 
have been evaluated. It has been pointed out that these are only 
measures for statistical information and some sort of topological 
information but have not taken into consideration of the spaces 
symbols occupied and spatial distribution of symbols. As a 
result, a set of new quantitative measures is proposed, i.e. for 
metric information, topological information and thematic 
information. In these measures, Voronoi region of map features 
play a key role, which not only offer metric information but also 
some sort of thematic and topological information. Experimental 
evaluation is also conducted. Results show that the metric 
information is more meaningful than statistical information and 
the new index for topological information is also more meaningful 
than the existing one. It is also found that the new measure for 
thematic information is also useful in practice. 
Quantitative measure for information contents of maps is an 
important issue in spatial information science. It has bee used 
for comparing the information contents between maps and 
images, maps at different scale, evaluation of map design and so 
on (Knopfli 1983, Bjorke 1996). Effective quantitative measures 
are of great importance not only for understanding the 
characteristics of spatial information but also for the effective use 
of spatial information. 
ACKNOWLEDGEMENT 
The work described in this paper was supported by a grant from 
the Research Grants Council of the Hong Kong Special 
Administrative Region (Project No. PolyU 5094/97E). 
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