April - June 2006
Development was jump-started by using an Esri site starter for ColdFusion MX. From a system point of view, Ortho Viewer consists of an ArcIMS mapping server, an ArcSDE geodatabase, and a ColdFusion MX application server. All of the image layers were loaded into an ArcSDE geodatabase that runs on Microsoft SQL Server. The ArcIMS map service runs on an IBM blade server running ArcIMS 9 and exclusively uses SDE layers for performance. The map service is set with a complicated suite of group renderers with scale-dependent thresholds.
The Web application runs on ColdFusion MX and uses the Mach-II framework for a clean and maintainable software architecture. The business logic is coded in reusable ColdFusion components. The Esri Java Connector is used by the ColdFusion MX application server to communicate with the ArcIMS mapping server.
Ortho Viewer gives the user four ways to quickly and easily find a location. The address dialog box uses the ArcIMS Java Connector to geocode addresses and intersections on the fly. The parcel dialog box provides a quick search by parcel number. The places of interest dialog box uses the USGS place-name dataset to give users a quick search by keyword. Finally, the bookmarks dialog box gives frequent users a way to store favorite locations to their computer using cookies. Ortho Viewer makes it easy to turn layers on and off, but for performance reasons, only four layers can be checked on at a time. Preset categories make it easy to select layers quickly.
Metadata is necessary for effectively using GIS data. Clicking on a layer's name in Ortho Viewer invokes the metadata for that layer. Users can also compare the metadata for every layer shown by clicking the Compare Metadata button below the layer list.
Ortho Viewer saves PDF files for printing and archiving using the open source Apache Formatting Objects Processor (FOP) Java library. Apache FOP takes an XML file and transforms it into a PDF file using an XSLT style sheet. Ortho Viewer can also save to a JPEG and PNG by using Java 2D technology, which allows the application server to dynamically generate images in memory.
The Ortho Viewer is an intranet Web application that Pierce County designed to view temporal changes in imagery. The viewer allows users to explore multiple years of imagery for locations throughout the county. This description of the process required to design the Ortho Viewer underlined the importance of focusing on a specific problem and using design elements to make an application more intuitive and user-friendly. It also illustrated that many servers and languages are typically needed to implement a GIS on the Web. For more information, contact
About the Author
Jared Erickson is a GIS Certified Professional (GISP) who has worked for Pierce County, Washington's Information Technology department for six years. An archaeologist by training, he specializes in application development of spatially enabled Web sites.
Tufte, Edward R. The Visual Display of Quantitative Information. Cheshire, Connecticut: Graphics Press, 2001.