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International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B2. Istanbul 2004 
functions, i.e. to serve as index to further information by 
making the symbols "clickable" (Figure 8) and to provide extra 
information by "mouse-over" (Figure 9). By using the 
clickable symbols, photographs, drawings, texts, sounds or 
other maps can be linked. This makes web mapping a more 
and more popular way of providing information to a large 
group of users, country-wide or even world-wide. 
   
  
    
2 « 
(a) "Clickable" map symbols as index 
Geoinformatics, 
sw, Cartography and Visualization 
   
(b) New map pop-out after clicking a key 
Figure 8 Map symbols as index to further information (van de 
Worm, 2001) 
  
Population numbers and age in 1990 
Overijssel 
  
Population (pers.) 
MS 
70000 
30000 
  
   
  
  
  
(a) "Mouse-over" map symbols with highlight 
2 
A 
  
  
  
Population numbers and age 
Overijssel 
  
  
  
(b) Extra info displayed when mouse is over a symbol 
Figure 9 "Mouse-over" map symbols to reveal extra 
information (van de Worm, 2001) 
In the case of maps for navigation, such information as traffic 
condition, landmarks, bus station, taxi station, road signs, larger 
scale maps, and so on can be linked by using clickable symbols. 
7. CONSIDERATIONS OF THE EFFICIENCY OF 
SPATIAL ANALYSIS OF WEB MAPS FOR 
NAVIGATION PURPOSE 
When incorporating with spatial analysis functionality, a 
selection of client-side or server-side Internet mapping systems 
has to be made to balance performance and functionality. For 
example, in the multi-modal public transport equerry system by 
Pun-Cheng et al (2004), some spatial analysis functions have 
been implemented as follows: 
> whether there is a direct route given the origin and 
destination as depicted on a map or by textual input; 
> whether one or more transfers are needed and what the 
options are; 
> how to get to the pick-up and drop-off locations (the 
stops/stations/piers) from the user's chosen origin and 
destination; and 
> how much the trip will cost, when and how frequent the 
routes are, and so on. 
An Internet Mapping System (sometime referred to as a Web- 
enabled GIS or an Online GIS application) is a Web application 
fully charged with GIS functionality. Usually, the applications 
emerge when traditional GIS packages are extended to support 
the Web technology. Basically, an Internet Mapping System 
follows the Client-Server Model with Web browsers as the 
clients and the Web site serving the application as the server. 
There are two variations to the basic Internet mapping 
application: (a) client-side; and (b) server-side applications 
(Gifford 1999). In the former, the client machine takes up all 
of the responsibilities of processing analysis functions. In the 
latter, on the other hand, the server platform handles highly 
process-demanding requests from clients 
In general, the client-side solution provides a better working 
environment with powerful functions for analysis. This 
approach is favourable for a smaller group of sophisticated 
users who are looking for complicated analysis functions. To 
achieve the best performance for this approach, additional add- 
on components (or plug-ins) for the Web browser need to be 
developed and extra effort to maintain software and plug-ins is 
also required. On the other hand, the server-side solution offers