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SPATIAL DATA TRANSFERS AND STORAGE 
IN DISTRIBUTED WIRELESS GIS 
Meng Lingkui!, 
Lin Chengda!, 
Shi Wenzhong” 
1, School Of Remote Sensing And Information Engineering, Wuhan University, Hubei Province, China, 430072 — 
(Ikmeng@public.wh.hb.cn linchengda@wtusm.edu.cn) 
2, Department Of Land Surveying And Geo-Informatics, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong 
(Iswzshi@polyu.edu.hk) 
Commission VI, WG VI1/4 
Key words: Wireless GIS, Spatial Data Transfers, Mobile Database, Dynamic Replication 
ABSTRACT 
There has been a great development in Wireless GIS (WGIS) new century. Spatial data transferring and storage in GIS is developed 
from wired to wireless network. This paper first briefly introduces the technologies and strategies of spatial data transferring and 
storing in distributed Wireless GIS. Second, the schemes of spatial data transferring modes in wireless GIS for improving the 
network transfer rates is introduced emphatically, and the distributed transferring process technology of GIS spatial data are also 
discussed. Based on these, we present the storage strategies in wireless database, and introduce mobile computing conception and 
three-tiers wireless replication database. Here, we emphasizes on dynamic replication strategies and methods in wireless 
environment. Finally, we compare several of data storage strategies in WGIS databases and the dynamic multi-tiers replication 
strategy is proposed for wireless database storage. 
1. INTRODUCTION 
Stand-alone and wired GISs may not meet the requirements of 
all the GIS applications appropriately, especially when users 
need to access a GIS time and location independently. 
Therefore, there is a need to move towards ubiquitous GISs, 
which can serve users anywhere and anytime. 
These days, not only GIS experts but also ordinary people tend 
to access spatial information using wireless equipments. With 
the rapid development of new integrated techniques, there are 
also many new achievements in GISs. The development of the 
handheld devices, such as PDAs, Java-enabled mobile phones, 
and laptop and Internet techniques, the application field of GIS 
has been enlarged and furthermore, this leads the new 
challenges to GIS techniques. GIS based on wireless devices -- 
wireless GIS (WGIS), will become a new branches of GIS and 
bring the GIS into a new stage of development. 
The technology of spatial data transferring and storage in GIS is 
developed from wired to wireless network at present. It is 
feasible for itinerant or peripatetic users to travel from one 
place to another by using the wireless network. 
However, in the applications of wireless network, the speed of 
transaction is getting faster, and the capacity of storage is 
getting larger. However, there is limitations in wireless GIS. It 
is a challenge task to connect network elements by radio waves 
instead of wires. For example, GIS spatial data transfers and 
Storage based on wireless LAN are restricted to spatial data 
capacity and transferring distance. Therefore, there exists 
deficiency on the data processing. It is potentially to solve the 
problem by using distributed dynamic multi-tiers spatial data 
transferring. 
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Wireless GIS technologies offer a lower time-to-market 
comparing to many wired technologies, which require the 
deployment of large amounts of new network equipments. The 
wireless GIS can not only satisfy the network demand of 
various personal digital assistants (PDAs), and portable 
computers at anytime and anywhere, but also can be regarded 
as the compensative means for traditional wired GIS. The data 
process is promoted through improving the transferring rate. 
2. CHARACTERISTICS OF WGIS 
In the mobile communication area, GIS network were usually 
divided into two types according to the wireless connection 
technology. One is based on the Cellular Infrastructure 
connection technique, which is also used for Mobile GIS; the 
other is based on wireless LAN techniques. Wireless network is 
a network, which is built, in a mobile environment, or the 
environment-combined wireless with wired. It is quite 
convenient for data-transferring network. Therefore, we first 
need to consider the characteristics of wireless GIS that will 
likely affect our way of working and thinking on the current 
GIS technology. ) 
  
  
       
  
  
Wireless GIS Spatial 
GIS Database 
le Server 
  
  
  
Mobile 
Equipment 
  
Fig. 1 Wireless GIS framework 
As illustrated in Fig.l, WGIS is composed of mobile 
equipments, wireless GIS server and GIS spatial database. The