PRODUCT COMPARISON FOR GIS OVER THE WEB: by Dv6b8Q

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									PRODUCT COMPARISON FOR GIS OVER THE WEB:

                ESRI’s ArcIMS

                      vs

        Intergraph’s GeoMedia WebMap




            Political Economy 6383

      Management & Implementation of GIS

                 Dr. R. Briggs

              November 8, 2001




                     By:

                James Janning

               Michael Wallace

                Justin Johnson
                                                                           Web-based GIS 1



                                  INTRODUCTION

       Web-based GIS is fast becoming the way to distribute geographic data to users

without the need of GIS software or specialized training for the end user. With nothing

more than a standard Internet browser, users from different organizations and

departments can view and manipulate geographic data from multiple sources that was

once only available to a select few (people who new how to use GIS data browsers and

had access to one).

       This paper will examine both basic principles of web-based GIS, the software

requirements of both the server and the end user, what types of data can be used, and the

data format that the client will receive. It will then take a detailed look at two products

being offered by the industry leaders in the GIS market. The first product, ArcIMS, is the

latest incarnation from ESRI for serving data over the Internet or an intranet. The other

product, GeoMedia WebMap is Intergraph’s first foray into the web-based GIS Market.

                          BASICS OF WEB-BASED GIS

       A successful implementation of web GIS requires the incorporation of clients,

middleware (application server connectors and web server software), web GIS software

(ArcIMS or WebMap), data, and physical server(s). The web GIS software provides the

tools necessary to manage GIS data so that it is accessible to clients through the Internet

and intranet connections. It does not directly interact with the client. An application is

necessary to act as a mediator between the user who is requesting information and

ArcIMS or WebMap, which retrieves it. Middleware, the web GIS software, and data all

reside on one or more physical servers. The client accesses the Internet or intranet using
                                                                           Web-based GIS 2



a web browser via http and TCP/IP technology. They can then contact the server and

request data from ArcIMS or WebMap through the middleware tier.

       When a client requests information over the web, the middleware applications

will process this request and pass it to the web GIS software. The web GIS software will

query a spatial database for the appropriate spatial and/or attribute information and pass it

back to the application. The application translates the information to a format that the

client can read and passes it back over the intranet or Internet.

       The responsibilities of the Map Serving application include sending and receiving

data between the client and application, organizing requests made by multiple clients,

managing data transmission and maximizing the efficiency of the server tier. The

application also determines what information is available to be distributed. The

application sets what colors and line weights each feature will be. It also determines in

what order the features will be drawn. In addition, the application will set the coordinate

system and units that the data will be viewed in.

       Web pages can be custom written to suit the needs of the individual organizations

using web-based GIS. Both ArcIMS and WebMap also come with application generators

that can be used to create generic templates for a quick implementation.

                                    DATA OUTPUT

       ESRI’s and Intergraph’s web products can send data to clients over the web in one

of two ways, raster or vector. Each of these formats has advantages and disadvantages

and it must be decided at the time of coding which format will be served.
                                                                           Web-based GIS 3



       When data is transmitted over the web in a vector format it has a “static”

connection back to the source. A picture is taken of the features that the client wants to

see and sent to them in a JPG, PNG, or GIF format. If the user does anything to change

the data (such as turning on additional features or zooming in on a specific area of the

map) the server must then request new data and another static picture taken and sent to

the client. Raster based websites are more server intensive because each request made by

the client requires the server to render a new image and temporarily store the image. The

main advantage, however, is that the communication between the browser and the server

is simplified and the middleware can execute these procedures rather quickly.

       When data is transmitted over the web in a vector format it has a “live”

connection back to the source. Features can be turned on and off and display scales can

be changed on the fly. Vector maps contain intelligent features linked to records in the

database, as do Raster maps. Vector based websites are less server intensive than raster

based websites, due to the use of vector data streaming. With vector data streaming,

Internet bandwidth and traffic will determine data rendering efficiency. In order for a

client to utilize a site designed to stream vector data, they must have a program locally

installed that is designed to render the data being sent to them by the server.

                                   ESRI’S ARCIMS

Introduction

       Since 1996, ESRI has honed a software product enabling GIS professionals the

functionality of gathering, viewing, manipulating, and disseminating GIS data layers via

a web browser. In May of 2000, ArcIMS (Internet Map Server) became the primary ESRI
                                                                           Web-based GIS 4



product for web-mapping solutions, replacing, combining, and extending the power of

two earlier products - MapObjects IMS and the ArcView IMS extension. This extremely

robust software product allows users to provide GIS solutions over an intranet, via the

Internet, or through a network (if ESRI client software is used as a browser in the place of

a standard web browser).

Application

       There are four connectors available for use as middleware: ActiveX connector,

Cold Fusion connector, Java servlet connector and WMS connector. The Java servlet

connector is the default connector that will automatically be selected during installation

unless one of the other three connectors is manually selected. The page developer might

select one of the other three connectors, which would work in conjunction with already

existing web development software.

       The ArcIMS software is comprised of four separate software tools. Together

these tools manage spatial data, process requests from the middleware, return responses

to the middleware and provide an interface for the administrator to develop web pages.

       The first three tools are ArcIMS Author, ArcIMS Administrator and ArcIMS

Designer. Together they are used to create a web page that contains an interactive map

made up of GIS data layers. Within these tools, decisions are made about what specific

GIS data appear in each map, what symbology will be assigned to the data layers, the

level of usability that will be offered to the end user as well as the layout of the web page.

The fourth tool is ArcIMS Manager. This tool utilizes Internet Explorer to provide the

developer access to the other three tools. Manager is only available if IMS Application
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Server is loaded on a Windows platform and allows for remote administration of

ArcIMS.

Data Input

          Arc IMS can utilize GIS data in ESRI, such as shape files and coverages, or from

an ArcSDE layer. Also ArcIMS can render images including aerial photographs and

satellite imagery. If a user wishes to incorporate GIS data in a non-ESRI format, the data

must be converted first. Further, ArcGIS desktop products can utilize as a data source a

data layer from an ArcIMS website.

Data Output

Raster:

         Distributed in JPG, PNG, or GIF format

         Requires no additional client-side software

Vector:

         Distributed with vector data streaming using ArcXML

         Requires that the clients web browser can interpret ArcXML and handle java

          scripting

Advantages

         Out-of-the-box usability

         Capability of administering server software from remote location

         Can act as a data source for other ESRI GIS software products

         ArcIMS is not limited to a Windows platform.
                                                                       Web-based GIS 6



Disadvantages

      Inability to use non-ESRI data sources without conversion

      Limited customizability without for-knowledge of Web-programming

       technologies

Server Requirements

      Microsoft WindowsNT, Windows2000, UNIX, or AIX

      Appropriate web serving software, such as IIS or Apache for the operating system

       selected

      Servlet engine

Client Requirements

      Microsoft Windows platforms, UNIX, or AIX

      Browsers that can handle java code, such as: IE 4, 5, 5.5, and Netscape 6 (for IMS

       3.1)

      Plug-in to handle ArcXML (extendable markup language)

Pricing

      $7,500 for 1st CPU

      $5,000 for each additional CPU

                  INTERGRAPH’S GEOMEDIA WEBMAP

Introduction

       Intergraph provides two powerful products used to disseminate geographic data

over the Web, GeoMedia WebMap and the more robust GeoMedia WebEnterprise.

GeoMedia WebMap allows the user to create web-based mapping applications that
                                                                         Web-based GIS 7



combine, analyze, and distribute GIS information from multiple sources over an intranet

or Internet. With WebMap the user can select what data is viewed over the web and print

maps. WebEnterprise combines all the functions of WebMap with the added feature of

manipulating geographic data.

Application

          An application generator is provided with both WebMap and WebEnterprise. The

application generator creates templates used to distribute data over the web. Applications

can also be custom written to meet the specific needs of an organization. These custom

applications may be written in a number of programming languages such as Java and

Visual Basic.

Data Input

          WebMap and WebEnterprise are able to view any data regardless of data format

or coordinate system. They use no proprietary data types or languages. WebMap and

WebEnterprise have the ability to view multiple data types with multiple coordinate

systems at the same time. Data in different formats are translated and reprojected at the

same time and viewed all at once in a coordinate system defined by the application. Both

products are also ideal for integrating aerial and satellite images.

Data Output

Raster:

         Distributed in JPG, PNG or GIF format

         Requires no additional client-side software

Vector:
                                                                        Web-based GIS 8



      Distributed in CGM (computer graphics metafile) format

      Requires ActiveCGM plug-in on the client-side. This program must be

       downloaded and installed by the user. The plug-in is limited to a Windows

       platform using IE or Netscape

Advantages

      Open GIS solution that uses no proprietary languages or data formats

      Ability to customize applications for specific clients

Disadvantages

      The CGM plug-in is a major component of WebMap (when viewing vector) but

       Intergraph (the maker of WebMap) does not own it

      The CGM plug-in is necessary to view vector data. The plug-in must be actively

       downloaded and installed by the client. If the client is not very computer savvy,

       this can cause problems

      CGM plug-in only works on Windows platform

      Limited customizability without for-knowledge of Web-programming

       technologies

Server Requirements

      Microsoft WindowsNT, Windows2000, or WindowsXP

      Microsoft IIS for the appropriate operating system

Client Requirements

      Windows98 or greater

      Microsoft Internet Explorer 4.0 or later
                                                                         Web-based GIS 9



      Netscape 4.7 or later

      InterCAP ActiveX control for ActiveCGM (for MS Internet Explorer browser)

      InterCAP ActiveCGM plug-in (for Netscape browsers)

Pricing

      $10,000 for two CPUs using GeoMedia WebMap

      $24,000 for two CPUs using GeoMedia WebEnterprise

                           CONCLUDING REMARKS

       There are many software applications available for the distribution of GIS images

over the Internet; among them are Intergraph’s GeoMedia WebMap and ESRI’s ArcIMS,

which by far hold the most significant market share. Pricing of each package is similar

on the surface; however, many hours of programming are required just for the basic

operation of WebMap. Conversely, a great deal of man-hours can be saved with

WebMap’s elimination of the need for data conversion. Each of the aforementioned

issues needs to be addressed from a cost/benefit analysis standpoint prior to deciding

which product to purchase. WebMap must be programmed prior to use, whereas

ArcIMS, although it too can be programmed and customized, comes with templates for

out-of-the-box usage, which can be extremely beneficial for an organization without the

budget for a full-time programmer.

								
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