Web-Based GIS Migration: How to Get Your GIS Data and Applications to Your Users and off All Those Computers

Web-Based GIS Migration: How to Get Your GIS Data and Applications to Your Users and off All Those Computers

The City of Aurora, the third largest city in Colorado, has developed numerous applications based on MapObjects, ArcView GIS, and ArcInfo development environments. Each application has dependencies and architectures that require significant time and effort by GIS professionals to maintain. The promise of Web-based GIS applications has brought about a major change in delivery of data and analysis. No longer does the GIS analyst have to physically deliver and install applications to the casual user. This paper will discuss the methods that the City has undertaken to transfer its PC-based applications to an Intranet-based system. System resources, architectures, and personnel will be described in detail as well as the problems faced in the migration.

The City of Aurora is the third largest city in Colorado. The population is approximately 260,000 with a total annexed area of 141 square miles. As will many cities in Colorado it is experiencing rapid growth and tremendous pressure to provide spatial information to the employees and citizens.

The City has a mature GIS system in place. Since the early 1990's the converted basemap has been in use. Several departments have contributed to the maintenance of the data as well as application development. A number of applications have been developed using Arc/Info AML code to produce automated mapping products. The majority of users of GIS products use paper maps. In addition there are approximately 50 to 100 users of ArcView at any one time. Several ArcView applications have been created that perform specialized functions. These applications have to be routinely maintained on the users desktop which puts a burden on the GIS support staff. What was needed was a way to distribute these applications to more of the staff and eventually citizens while maintaining control over the development and deployment. This is where GIS on the internet has proved to have great potential for spatial data distribution.

The web based application prototype has its new architecture compare to the desktop GIS applications. Web based GIS applications are thin clients. The end user only needs a web browser to access GIS data and functions over the Internet. The GIS applications and data are resided on the server side. Therefore, it is the most efficient way to deploy and maintain the GIS applications. In addition, it reduces hardware and software cost from the client’s machine and less training effort for the end users.

After a review of the potential GIS applications that could be web enabled, it was decided that both ArcView IMS and MapObjects IMS were to be purchased in 1999. This would allow the one staff developer to leverage her expertise in both Avenue and Visual Basic programming. Several prototypes were developed from a basic address/location look up to a porting of a complex crime analysis program.

The importance of having an intranet/internet infrastructure and development team in the organization was quickly discovered. GIS intranet/internet applications should not stand alone. They must be a part of the overall enterprise intranet/internet strategy. The organization did not maintain an in-house web site, it was contracted out. This in 1999 was a wise strategy due to the great work load on the Information Technology staff to prepare for the year 2000 conversion. The additional skills that an IT staff can bring to web enabling GIS were not available early on.

While staff had advanced knowledge of Avenue programming and some development expertise with MapObjects, the web authoring skills had to be learned as the applications were developed. A comparison of the three Esri IMS products is shown in Table 1. The additional programming language that needed to learned was JavaScript. Several training classes were required to become familiar with the basic implementation of this language. At the time of consideration, only ArcView IMS and MapObjects IMS were available. When the ArcIMS product becomes available, the new language ArcXML will have to become a part of the languages that the developers know.

An issue in deciding on which GIS web product to use is the hardware platforms in place in the organization. While the City of Aurora has several HP UNIX servers a quick look at Table 1 indicates that the preferred development platform is Windows NT. The development and testing of the applications was conducted on the users NT workstation. This became a performance issue with users testing the application and the developer trying to conduct other business. The purchase of a stand alone GIS web server is planned but still has not been delivered. The preferable configuration would be a single processor 550Mhz box with a minimum of 256Mb RAM and a video graphics card that can display images with high resolution. Additional processors and RAM could be added as the load demands.

Performance issues between the two products were considered carefully. Reports were that for multiple concurrent users the ArcView IMS would suffer long refresh times. This would not be so bad with the specialized programs that would only have a few users at a time. The high volume, "what and where" applications would be developed using the MapObjects IMS product. Three applications were developed. The first was a simple MapObjects address look up. The second application was a porting of an ArcView program that was developed for the Planning department. This project allowed the user to use several different types of location queries to find out information about a location. The third application, GCAP is described below.

The Geographic Crime Analysis Program (GCAP) is one of the desktop GIS applications being converted to the Internet mapping application using ArcviewIMS. The web site is comprised of multiple servers. There are data servers, a web server and an application server. The data server stores the GIS shapefiles and the crime incidents database. The web server and application server are integrated on one computer (see Figure 1).

The GCAP web application provides general-purpose mapping tools including: zoom in, zoom out, pan, fullview and identify, and specialized crime query tools. User can query crime incidents based on the time and location. For example, the system can query and display city-wide crime incidents that happened yesterday.

Figure 3. GCAP Query Return Screen

The development tools used to develop this application including client side language and server side languages. Client side languages are HTML and JavaScript, which are used to build the browser interface. Server side language is Avenue script.

There are quite a few challenges we have encountered during the development process, such as data updating and image distortion as served over the web.

GIS intranet/internet applications are the most efficient way to get spatial data to the largest number of users. The users like the ease of having an easy to use application that they can access with a familiar browser. The development staff and system administrators like the ability to have only one application to maintain.

The challenges are that the skills required to develop and serve GIS web based products are beyond most of the current GIS professionals. They require assistance from IT staff trained in internet technology. With this team approach the GIS web application becomes a part of the overall enterprise web strategy.

The City of Aurora has prototyped several applications on the web but has not conducted a full scale roll out of a production application. With the release of the ArcIMS product, the City can take advantage of the new architecture and jump in with both feet.

Xin Lu

GIS Specialist

City of Aurora/Info. Tech Department

15001 E. Alameda Dr.

Aurora, CO 80012

Xlu@ci.aurora.co.us

Dave Murray

GIS Coordinator

City of Aurora/Info. Tech Department

1470 S. Havana St, Ste 722

Aurora, CO 80012

Dmurray@ci.aurora.co.us