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Published in Geomatica, Vol. 53, No. 4, 1999

Facilitating Digital Spatial DataTransactions Using An Online Tool

Iestyn Polley Research Fellow email: i.polley@eng.unimelb.edu.au and, Ian Williamson Professor of Surveying and Land Information email: i.williamson@eng.unimelb.edu.au Department of Geomatics The University of Melbourne Parkville, Australia

Abstract

This paper presents an online system that facilitates digital spatial data transactions.

The methodology used was to case study the requirements of one typical spatial data

system, to determine its digital handling needs, and to implement and study a solution

to these needs. The case study is used to demonstrate that efficient digital data

handling methods are needed, and that these needs can be addressed through

appropriate use of technology such as the Internet and the World Wide Web.

The use of Internet for digital spatial data dissemination and integration purposes is

described, along with the implications for the types of user of this spatial information.

There is particular reference to using two-way flows of data to allow data custodians

to receive digital data as well as to disseminate it. The prototype was constructed with

these requirements in mind, illustrating the accommodated spatial processes and

implementation considerations. The paper assesses both the presented concepts and

the implementation itself.

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Introduction

“There is no doubt that the Internet is changing the way in which we

get access to information and the volume of data that is at our

disposal. The Net affects the way we learn and the way in which we

practice our business.”

(Dale, 1998)

The Internet has allowed spatial data providers unprecedented opportunity to

disseminate data, and conversely, has allowed users unprecedented access to volumes

of spatial information. The development of tools that allow presentation of spatial

data through the Internet has enticed more and more spatial data providers to add the

Internet to their data dissemination methods. Meanwhile, a coordinated and

premeditated approach to the dissemination of important spatial data has resulted in

the emergence of Spatial Data Infrastructures (SDIs). The increased availability and

use of digital spatial data unavoidably requires data handling processes between

parties, especially those tasked with maintaining and presenting data, to become more

efficient. The need to distribute digital data, and the need for data maintainers to

acquire digital data, precludes the use of digital networking technologies, such as the

Internet, which can address digital data handling needs.

This paper introduces an approach to facilitate digital transactions in spatial data

through the Internet, and more specifically, the World Wide Web (WWW).

Background issues and concepts, including the growing focus on spatial data

provision within a SDI, and the Internet's role in disseminating digital data, are

presented. A case study of the Victorian cadastre is also presented, demonstrating

specific key issues associated with handling digital spatial data. A prototype spatial

data browser is introduced, demonstrating the traditional data dissemination role of

the Internet (a 'one-way' data flow model), and providing an extended role that better

addresses the needs of spatial database custodians (a 'two-way' data flow model). The

technical concerns with the prototype are reviewed in some detail, as are the major

players in the digital spatial data system and how they are facilitated by the prototype

implementation.

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Proliferation of Digital Spatial Data

The traditional role of the cadastre has been to support the land market. More recently

it has fulfilled a role in developing SDIs as a contributor to land related data,

especially since the advent of digital media and economic rationalistic tendencies in

some jurisdictions (Williamson et al., 1998). Meanwhile, it is perceived that the

cadastre of the future will incorporate information more relevant to the changing

perceptions of use of land and the use of land related information for varying purposes

(Kaufmann and Steudler, 1998a; Kaufmann and Steudler, 1998b), leading to

increased use of the underlying datasets. The cadastre's maintenance processes are

responsible for the maintenance of the cadastral map, and therefore the efficiency of

an SDI that relies on a cadastral basemap is partly reliant on the efficiency of the

cadastral system itself.

There has been some redundancy in the amount of time spent in collecting and

organising digital data, and many institutional arrangements are struggling to keep up

with the pace of technical progress (Heikkila, 1997). Many cadastral systems are

similarly struggling to appropriately and efficiently handle digital data and processes.

Investigations into modifying cadastral data maintenance processes are being

undertaken in different parts of the world (Enemark, 1998; Jacoby and Marwick,

1997), while digital lodgement of survey plan data as a part of cadastral processes is

also being seriously studied. Spatial data processes are becoming more efficient in

order to accommodate the growing need for spatial data, particularly processes that

are still 'going digital'.

Case Study - Digital Information Handling and The VictorianCadastre

In the Australian state of Victoria, digital spatial data usage has become more

widespread, stemming from the fact that about ninety per cent of all government

information has a spatial component (Geospatial Policy And Coordination, 1997). The

State Government has helped make spatial data more available, especially the state

maintained digital cadastral map or Digital Cadastral Database (DCDB), as a result of

wider economic rationalistic strategies (Williamson et al., 1997) (Williamson et al.,

1998) and desire for process efficiencies within government (Grant and Mooney,

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1997). More information about the State of Victoria's Spatial Data Infrastructure and

the development of the DCDB are covered by Williamson et al. (1997) and (1998).

The Victorian State Government strives to be commercially competitive and recoup a

return on the services or products that are provided. An example of this is the

maintenance and provision of Victoria's DCDB, which, being a digital representation

of the geographic land parcel information across the state, is sought after as a spatial

base layer by many data custodians and resellers. The value of the DCDB is such that

it now features prominently within the cadastral system, as part of the cadastral

maintenance process. The processes that accompany the day to day operation of the

DCDB are subsequently desired to be as efficient as they can be, in order to be able to

more efficiently support the DCDB, it's users and processes.

Previous to these efforts, problems were encountered which made use of the DCDB

undesirable or impractical for some users. A review of digital cadastral map base data,

and users of that data across Australia in 1995, identified that many digital cadastral

databases experienced problems not only with data quality but also with data updates

and upgrades (Wan and Williamson, 1995). Because of these problems, many

organisations maintained their own stores of hardcopy maps of parcel or property

based data, often in duplication with map bases held by other organisations. In

recognition of this, the Victorian State DCDB custodian has recognised that providing

better access to an improved DCDB, would provide a means for many users to reduce

their costs by using the new format DCDB as a base for their own data instead of

maintaining their own cadastral datasets (Geographic Data Victoria, 1997).

Digital spatial data use and handling is becoming more important, which is

demonstrated by:

- the commitment made by government to the reforming of the DCDB; and,

- the reforms being applied to spatial data handling processes to more efficiently

handle digital data.

Players in the DCDB area, require:

- easy access to the DCDB;

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- data in digital form rather than traditional hardcopy mapping; and,

- digital data handling strategies, many of which closely affect the datasets of

custodians and plan approval authorities.

A digital environment that allows digital handling of spatial data can be

accommodated in a variety of ways, most obviously through the Internet. Given the

current Internet technology, it is possible to:

- Provide access to digital custodian data. This already occurs in a variety of other

different jurisdictions and disciplines (there are some examples in the next

section);

- Enable data submission. This enables the transfer of digital data from user to

custodian, in support of custodian needs to acquire updated and/or upgraded

information from data suppliers (for example, private surveyor);

- Enable complete digital handling of data. Any remaining hardcopy transfer

processes which degrade the quality of stored digital data are avoided; and,

- Enable efficient handling of digital data. Allows the data transfer process to

become more efficient, since all data functions can occur remotely through the

same interface. This aspect is one that is achievable through appropriate use of

technology, as demonstrated in the following parts of this article.

Digital Spatial Data on the WWW

At the present time it is possible to set up a GIS-like front end from within a web

browser, and allow users to perform queries to some remote database. Many examples

of those that deal with spatial data exist already, for example the Environmental

Resources Information Network (ERIN) (Environment Australia, 1999; Freeman et

al., 1998), the Western Australia Land Information System (WALIS) (Taylor and

Burke, 1998; WALIS, 1999), the Australian Capital Territory's online mapping

service (ACTMAP) (Collins, 1998), Terranet New Zealand’s Property Information

Service (TerraLink, 1998), and the Canadian Province of New Brunswick’s Real

Property Information Service (Finley et al., 1998), are just some. Peng (1997) and

Peng and Nebert (1997) discuss the various technologies involved in Internet GIS.

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Doyle et. al. (1998) also describe various Internet GIS technologies in presenting

spatial data through the Internet for urban and planning applications. Current models

for presenting database information through the WWW are similar, in that database

data more often than not reside somewhere on the remote database, which is accessed

by an intelligent client on the user's local computer across the Internet. These clients

have become practical and more user friendly with the introduction of browser plug-

ins, Java Applets and ActiveX objects, producing information tools that are relatively

powerful yet relatively intuitive to use for a variety of purposes.

The rise in popularity of the Internet on the back of the WWW has caught more than a

few unawares. Black (1997) wrote that:

“If it [the Internet] had been anticipated, the Internet and its requisite

languages, codes and protocols would most certainly have been

designed differently. The problem is that the technology was well-

established before the most compelling applications had been

envisioned”

In its earlier years, the WWW was marked by its lack of complexity and inability to

facilitate more complicated operations, such as those complementary to online GIS

applications. This included the presence of undesired latency between information

requests; lack of state between requests; lack of native vector display format; and

[initial] lack of security at the server side (Chopra, 1996). Other technical

considerations are that of network transfer rates, or security of transmissions such as

in protecting credit card details or proprietary data. Commercial vendors have been

quick to realise the potential of the WWW and have made efforts to overcome these

technical problems, through server and client software, GIS database linkages and

tools, and through Java, ActiveX, and plug-in software.

Latest vendor products have included lightweight GIS-like tools that remove some of

the complexity in the pursuit of user-friendliness. Products like MapInfo ProViewer

and MapInfo Mapplets for Microsoft Excel (MapInfo Corporation, 1998),

ArcExplorer (Environmental Systems Research Institute, 1998), and others are

customer/user oriented products that allow GIS data to be used more readily by

relatively inexperienced users. There will always be an undisputed need for serious

GISs, but tools that make GIS more or less transparent to the user will become more

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widespread. Their useability and hidden or limited complexity will make them more

attractive to casual users, and subsequently, a mass market.

There are also other non technical concerns arising from Internet data systems.

Concerns about privatisation of previously public data, brought on by the

development of WWW content, have arisen (Buttenfield, 1997). GIS may be

becoming a ‘popular commodity’, but issues such as proper use of data by uneducated

users and the quality of presented data remain (Barr, 1996). Perhaps it is essential to

either educate the mass market on how to use such ‘commodities’ properly, or to

make it so that the software prevents inappropriate or unauthorised use, or places

warnings, disclaimers, or guidelines on the use of data (through data licensing for

example).

Digital Spatial Data Flow Paradigms on the WWW

The WWW, with its graphical presentation abilities, its ability to deal with digital

information, its ability to reach remote users in real time, and its global audience, has

the potential to provide a streamlined spatial data dissemination and integration tool.

Nearly all WWW spatial data systems that are currently available from software

vendors, are data presentation systems only, that is, users are only able to receive data

from their custodian. This 'one-way' flow of data does not utilise the full potential of

the capability of the Internet, and does not allow spatial data producers such as land

surveyors to contribute their data to database custodians, who must rely on separate

means to commute their digital data. A 'two-way' flow of data that allows such spatial

data producers to digitally transmit their information would make better use of the

Internet infrastructure, and also allow complete digital handling of spatial data (see

Figure 1).

Users and Spatial Data Transactions

The range in the type of players in the spatial and cadastral systems can be

summarised by the functions that they contribute to the system as a whole. These

users include data producers, data custodians, large dataset customers and casual data

users. The functions that are performed by these users include:

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- download of data, possibly to provide base data for a GIS like application or

dataset;

- viewing of data, possibly as part of a general public information service;

- upload of user data, to allow simultaneous viewing or graphical comparison with

custodian data; and,

- submission of data, for use in updating or upgrading a digital dataset, which, could

be part of a digital lodgement component of a land registration system.

A number of projected users for the system include: the spatial data user, who may

periodically purchase data; the land surveyor (a spatial data producer), who may need

access to spatial data but is also able to submit new data as well; and, the casual user,

who would use the system for its simplest data enquiry services. The most significant

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example is that of the land surveyor, who potentially has the need for use of a two

way flow of data, both to and from a remote data custodian.

Land surveyor / Spatial Data Producer

This example is perhaps the most significant, as it demonstrates the 'two-way' flow of

data across the Internet. This example is that of the spatial data producer being the

user, who not only downloads data but also is able to upload or submit updated data

(see Figure 2). The most obvious use for this is for digital lodgement of survey plan

data, as part of a land registration process, or perhaps, the lodgement of a

Cartographer's digital map to a map server custodian. After submission, the digital

data is either redirected to the relevant place for further processing, or it can be

dropped directly into a database, depending on the custodian's adopted strategy for

handling digital data.

Spatial Data Customer

This example is that of the more traditional 'one-way' model of data flow through the

WWW, ie. a user who generally downloads portions of data for use in GIS as a base

data set. This type of user will use the system to select and retrieve data from the

database. Following this, the user will be able to either view or download the dataset

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to a local hard drive (see Figure 3). The system would be able to retrieve the data

from the relevant database and load it into the Java Applet on the user's computer.

The Applet would then be able to save the data into a file on the user's local hard

drive in a specified format. Purchasing conditions would normally apply, as would the

relevant security measures to ensure data integrity and privacy while in transmission

across the Internet. Limitations for this type of user are the size of data files, which

could take an inordinately long period of time to transfer for large files. For this

reason traditional data delivery methods, such as a hybrid CD-ROM mailout method

for example, may be needed to augment this process until network transfer rates

improve.

Casual User

The casual user would use the system for casual enquiries, mostly for single parcel

queries. In this case data download capability would probably not be necessary and

submission capability would not be appropriate. Providing for this type of user allows

data custodians to disseminate portions of their data into the community (see Figure

4). It should be noted that new and unthought of uses for the data will in all

probability appear, because its availability will attract new types of users and uses.

The effect that the availability of such data may have on society in general has yet to

be determined.

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Prototype for 'Two-Way' Handling of Spatial DataThrough the WWW

A prototype system to address these issues was implemented to enable online spatial

data transactions using a WWW browser. The system is invoked through a Java

Applet from a WWW page, and through a series of windows, allows users to perform

data transactions online. This system is not a definitive application, but a proof of

concept prototype that illustrates implementation issues, possible users and uses, and

generally how spatial data can be handled through the WWW using the 'two-way'

paradigm of data flow. It provides a more land surveyor oriented focus on database

updating, deriving a cadastral context related to that of the Victorian Cadastre and

SDI as presented earlier.

The description that follows concentrates on the WWW technologies that allow such a

delivery system to exist. Data transfer standards, database technologies and data

modelling within these contexts are not discussed in any detail, as they are separate

areas of research to the one contended in this article. The basic technical focus,

therefore, is directed at the particular technologies that allow the delivery of GIS or

spatial data at the point of the WWW browser.

The system follows a 3 tier client / server hierarchy, the type of which is illustrated by

Alexander (1997), and also mentioned by Strand (1997) in his overview of online GIS

components, and used in many other WWW-GIS applications. The WWW server

consists of a Common Gateway Interface (CGI) program that initiates a Java

application which then interacts with a database through Java Database Connectivity

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(JDBC) and Structured Query Language (SQL) queries (see Figure 5). The CGI

approach avoids problems that arise from accessing data servers through firewalls,

which ordinarily block more regular connection methods such as through TCP/IP

sockets, or through Java Remote Method Invocation (RMI) etc. The use of JDBC

allows the use of distributed data servers, thus increasing the protection offered to any

data server from the Internet. Database configuration files specify which network

users are allowed to connect to it, and what operations connected users are allowed to

perform, thus restricting access to all bar the CGI process on the WWW server (see

Figure 5).

The user interacts with the system through a Java Applet. Considerations for using

Java in online GIS applications have been documented by Wang (1997) and Peng

(1997). Java was used to develop the Graphic User Interface (GUI) as it was free,

widely documented, was supported more widely than the major competitor ActiveX,

and was easier to disseminate to heterogeneous platforms than browser plug-ins, the

other alternative. The Java Applet utilises vector display, typical view manipulation

(zoom, pan fit etc) and toggle of data layers (a layer is devoted to each data source).

Network transmissions are kept to a minimum by performing most functions within

the Applet's memory space on the client's machine.

A specific digital certificate was used to sign the Java Applet, for reasons which will

be discussed, which results in a user dependence on a particular brand of WWW

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browser. To date, different digital certificate schemes apply to each of the major

browsers, and although for this prototype system only the Netscape browser was

catered for, there is no technical reason why both major browsers can not be

supported.

The Applet accesses metadata about each of the available databases through a CGI

transaction with the host server. This information includes network location, available

data, dataset information and basic query information. The CGI program sends this

information back to the Applet, which then creates the dialogue window. This

window contains a panel for each available dataset, and each includes components

that allow the user to specify search criteria for data retrieval and display (see Figure

6). Upon request, the Applet either makes a request to the WWW server to retrieve

the data from the data server, or goes through a process to load data from the local

disk.

Remote data is sent across the network, through a CGI transaction between Applet

and host server, as a stream of data. The data stream consists of graphic instructions

which is created from data retrieved from the database by the CGI software. The data

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stream approach is used to avoid file caching on the user's computer, which occurs

ordinarily if a file is loaded into a WWW browser, and helps to control access to data.

Prototype Innovations

User Data Upload

Files can be loaded into the Applet from the user's local drive. This process is only

made possible through digital signing of the downloaded Applet code, and the

relaxation of specific Java Virtual Machine (JVM) Sandbox restrictions in a specific

browser. This introduces issues such as browser dependence and security issues that

will be discussed shortly. The file data is loaded into the Applet as a layer separate to

the server data and, likewise, can be toggled on or off as needed. Multiple files can be

loaded into the Applet at once.

Data submission has been incorporated to facilitate the updating of digital databases.

An example of such a practice is that of digital lodgement, which allows submission

of digital files by land surveyors as part of the land parcel registration process. No

particular submission or automatic database update strategy is adopted, although

specific strategies can be incorporated into program logic as needed. This prototype

proves that the process of digital submission of documents is possible, and only

requires an institutionally sanctioned procedure to allow its formal implementation.

The most logical extension of this concept is to allow the submitted data to be

automatically integrated into a digital database. This would allow automatic update

and upgrade of databases through the Internet to become a reality, although

technically it is already possible. There are unsolved issues relating to this that need to

be dealt with, including the aforementioned update and upgrade strategies, and the

infrastructural implications that any automatic process may have on data quality and

accountability for example.

Often due to the nature of database data, any update capabilities would be restricted to

registered users. A registered user, using the cadastral digital lodgement scenario,

would typically be a licensed land surveyor as defined by jurisdictional cadastral

surveying legislation. The use of user/password schemes to restrict entry, and the use

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of digital signing of submitted data files to prove data origin and authenticity, would

ordinarily be required.

Remote Data Download

Downloading of onscreen data to a local drive is provided for in the prototype.

Following negotiation of a user/password access procedure, data is saved in a chosen

format onto the user's local drive. As with data upload, the use of a digitally signed

Java Applet and relaxation of JVM Sandbox restrictions is necessary to allow this

operation to occur. Again, there are security issues associated with digital signatures,

browser dependence and fee/licensing issues associated with the downloaded data.

Avoiding Java Applet Restrictions

In order to allow the Java Applet to step outside the JVM Sandbox restrictions,

specific operations must be performed. These restrictions are relaxed only when the

Applet is signed with an object signing digital certificate, specifically generated for

signing object code. On top of this, the Applet must specifically request the user for

permission to relax particular restrictions, and only those that are requested are

relaxed. This approach means that the Java Applet can not make any unauthorised

access to the user's machine, and that all operations that request a relaxation in

restrictions do not occur unless the user approves. This procedure is specific to each

of the major brands of WWW browser, as currently code signing and relaxation of

JVM Sandbox restrictions occurs in versions of Java that are not yet supported by the

major browser vendors.

System Security - Digital Certificates

The Java Applet is signed with a X509v3 digital certificate, which has extensions on

top of the regular X509 structure to allow it to step outside of the Java Sandbox within

Netscape 4.x and later browsers (Netscape Communications Corporation, 1998). By

doing this, the Applet not only gains the ability to save and read files from the local

drive, it allows the user to authenticate the origin of the Applet and to provide tamper

detection on the Applet files that are downloaded from the server.

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Data files that are loaded into the Applet, or submitted to the server, would ordinarily

be digitally signed by the user, using a digital certificate. This provides tamper

detection and authentication capability on the data file, as would be required on a file

of survey plan data for example. This capability is not yet incorporated into the

Applet itself, but it would be desirable in a fully fledged application.

System Security - Session Encryption

The entire session would ideally be encrypted using some accepted encryption

scheme, such as Secure Sockets Layer (SSL) for example. This procedure would

make all network data transactions undecipherable to eavesdroppers, and would

enable commercial data transactions to be made safely. The encryption procedure

itself would require the WWW server software to be cryptographically enabled, and

would also require the server to have its own digital certificate. For any download,

upload and submission transactions to be made safely, the user must also have a

digital certificate.

Prototype Assessment

The system enables all parties to the operation of a digital spatial database to satisfy

their data transaction needs. Data users can certainly download their data online, as

with many online systems that are already available, but more importantly, players

more involved in the maintenance of the database can also perform their relevant

roles. In this latter case, data contributors can upload their data for integration into the

custodian's database. Utility and planning organisations that are important

contributors to the cadastral update process can retrieve and upload digital data as

they require. The short of it all is that data users can perform their spatial data

transactions digitally without recourse to more inefficient hardcopy methods.

The system as implemented is widely deployable and is intended to be simple enough

for all users. Security is a concern for determining both the authority of users, and the

integrity of data. The system itself demonstrates the 'two-way' flow paradigm that

allows more players in the spatial data handling processes to become digitally

capable, and takes the concept of online data systems that one step further. The

implementation of the system itself relies on digital certificate technology, which is

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still in its infancy, and also depends on good bandwidth to enable large transactions of

data and for favourable Applet download times. The system also needs institutionally

defined data handling procedures, as, especially in the cadastral case, the data and its

handling procedures carries legal ramifications. The system also needs to implement

procedures that should notify players when they can download data, and which data

they should download or actually have access to.

Conclusion

Over time, cadastral systems are becoming more and more digital. Existing hardcopy

systems are acknowledged to be struggling to efficiently support the existing

hardcopy processes given that a large amount of information is digital at many points

of its life within the cadastral system. The importance of digital spatial databases

within the system is increasing, especially as they are being used in many contexts as

base data for other information systems and SDIs, and have become a saleable

commodity.

To provide for the transaction of digital spatial data that would support database

maintenance and general data commerce, digital data handling methods are needed

and are being introduced widely. The most obvious contender to facilitate digital data

handling is the Internet and the WWW, which could enable data custodians to

implement a system that allows data handling processes to be conducted online. A

typical online spatial data application could provide data viewing access for members

of the general public, data purchasing of larger quantities of data, and facilities for

submission of digital plan data or digital lodgement.

Such an application should provide functionality typical of lightweight graphic

mapping applications, but should also provide extra functionality, such as data

purchasing or downloading for example. Data submission facilities should be

provided for the user if the system is to provide for the upload of digital data. Data

submission could supplant existing lodgement processes by simply redirecting the

user's data to the appropriate authority, who could then treat it as they would hardcopy

plans. Alternately, more sophisticated regimes could be implemented that utilise a

more automated spatial database update process. Access to certain functionality may

need to be restricted depending if the service attracts fees or requires that users be

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qualified in certain areas to be able to download data, or to upload data (eg a licensed

surveyor). Adequate security measures should be implemented to protect the

commercial interests in data, the privacy of information that may be attached to the

data, and to authenticate both users, data providers and transmitted data as needed.

The WWW, as a facilitator for digital data handling tools, has allowed spatial data to

become more available to a relatively large audience. This allows ordinary citizens

access to data that they would previously find difficult to obtain. In addition to this,

the Internet can provide an avenue for commercial data users to gain access to

purchased data. The advantages of such remote communications are generally

understood, although there are concerns about network limitations such as bandwidth

etc. The last point is that the Internet can be used to assist in the actual maintenance of

the spatial database itself, as it provides a digital medium that facilitates the

transmission of digital spatial data and can provide for such concepts as digital

lodgement for example. The pace of movements in the GIS industry and in the

Internet industry means that the technology to provide such functionality is available,

and the use of such systems, because of the information that they provide, is

becoming more widespread.

Acknowledgment

This research was made possible from a collaborative Australian Research Council

(ARC) grant jointly funded by Land Victoria and the Surveyor General's Department

New South Wales. The authors wish to gratefully acknowledge this support, however,

the views expressed in the paper are those of the authors and do not necessarily reflect

those of these organisations.

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22

Authors

Ian Williamson holds the Chair of Surveying and Land Information in the Department

of Geomatics at The University of Melbourne, Victoria, Australia. He holds

bachelor's, master's and doctorate degrees in Surveying and is a Registered

Professional Land Surveyor and a Chartered Professional Engineer. Professor

Williamson is a Fellow of the Academy of Technological Sciences and Engineering,

Australia, a Fellow of the Institution of Surveyors Australia, a Fellow of the

Institution of Engineers Australia, and an Honorary Fellow of The Mapping Sciences

Institute, Australia. Prior to his academic career, he worked for a state government in

Australia, an American engineering corporation based in the USA and ran his own

consulting practice. He was Chairperson (1994-1998) of Commission 7 (Cadastre and

Land Management) of FIG. He has consulted widely to state and federal governments

in Australia and overseas, United Nations agencies and the World Bank on

establishment of cadastral, land and geographic information systems. Professor

Williamson can be reached at the Department of Geomatics, The University of

Melbourne, Parkville, Victoria 3052, Australia. Ph.: +61-3-9344-4431, Fax.: +61-3-

9347-4128, E-mail: i.williamson@eng.unimelb.edu.au URL:

http://www.geom.unimelb.edu.au/people/ipw.html

Iestyn Polley holds bachelor's degrees in Geomatics with honours, and in Science

(Computer Science). He has also recently successfully completed candidature on a

master's degree in Geomatics at The University of Melbourne, which researched the

area of providing spatial information systems through the Internet. He has also

worked through non-academic periods as a research programmer dealing with

databases and the WWW, and as an applications programmer for a private survey

consulting company. Currently, he is a Research Fellow at the Department of

Geomatics at the University of Melbourne and has research interests in Internet and

spatial information systems, and lately in Internet delivered multimedia applications.

Mr I. Polley can be reached at Tel.: +61-3-9344-6881 Fax No.: +61-3-9347-4128, E-

mail: i.polley@eng.unimelb.edu.au