Internet GIS solution for Bermuda’s Environmental Health Department
GIS and The Internet
The problems of sharing data and resources have been concerns to GIS practitioners for a long
time [Palmer, 1984]. There are essentially two issues that need to be addressed to allow sharing.
One of them is a standard protocol for communication and another is a channel for that
communication to happen. The Internet and its related technologies have produced low-level
protocols and networking hardware. However, the GIS community had to solve much more
complex problems, namely standards on data and software interoperability, before data and
resource sharing could be realized. Although the GIS community was quick to take advantage of
the Internet -- the first GIS-L Internet list-server to share information was established in 1988 at
the State University of New York at Buffalo -- it took quite a while before this group enjoyed the
full advantage of networking.
Part of the reason is in the limitation of GIS software architecture that does not favour distributed
spatial databases. The main reason is the difficulty in establishing widely accepted standards in
data model and software interoperability. There were significant developments in both of these
areas recently at national and international levels, leading to specifications developed by the
OpenGIS Consortium and Technical Committee 211 of ISO. At the same time, the recognition
of the importance of spatial data infrastructures highlighted the need of data clearinghouses that
rely heavily on the Internet to store and manage descriptions of data (metadata) for users to
browse [Coleman and Nebert, 1998]. Together with the idea of distributed data, the concept of
distributed processing also became popular in the mid-1990s. Internet development, together
with the introduction of JAVA in 1995, made the creation of more intelligent clients for Internet
mapping possible [Nebert, 1994; Plewe, 1997].
Two Web mapping products that support the development of Java Clients are Spatial Fusion,
developed by CARIS, and ArcIMS, developed by ESRI.
ArcIMS
ArcIMS is an Internet GIS product designed to allow for GIS functionality to be distributed
across the Internet. Examples of GIS functionality available in a web-site created using ArcIMS
include [ESRI, 2001a]: (a) data querying – retrieve spatial/attribute information based on user
defined, or pre-defined, queries; (b) data integration – add local data along with the ArcIMS
served data in the Web browser; (c) buffer creation – select and buffer features; and (d) address
matching.
ArcIMS Architecture
ArcIMS has a multi-tier architecture consisting of a presentation, business logic and a data tier
[ESRI, 2001b]. ArcIMS also provides a set of tools for creating and managing an ArcIMS web
site, referred to as ArcIMS management applications.
The presentation tier consists of an ArcIMS client which is used to access, view and analyse
geographic map. In general, the ArcIMS client makes a request to a MapService residing on an
ArcIMS site. A MapService contains instructions on how to generate a map. Two types of
ArcIMS clients are an HTML Viewer and a Java Viewer – an applet running in a Web browser.
The business logic tier contains the components necessary to run Map Services and process
requests and responses from the other 2 tiers. ArcIMS communicates between the presentation
tier and the business tier using ArcXML. The data tier consists of the data sources available for
use with ArcIMS (e.g. ESRI Shapefiles).
Management Applications
ArcIMS includes three tools that allow users to create and manage an ArcIMS site. These tools
are:
-
ArcIMS Author – used to define (e.g. select, specify symbology, etc.) the datasets that will be
available for the ArcIMS Web Application; this information is stored in a MapConfiguration
file
- ArcIMS Administrator - used to publish (e.g. create) and administer a MapService;
MapServices are created from MapConfiguration files
- ArcIMS Designer - used to create an ArcIMS client – that is, a web site that the end users
will interact with.
