Low-cost Solution Delivers Gigabytes of Imagery Via the Web
Gary Ostroff

   For real estate professionals and geographers, location is everything, but presenting our knowledge of a place to clients, over the Web, can sometimes be a daunting challenge. CommunityCartography (ComCarto, www.comcarto.com) faced this problem when its customer, COMPS, Inc., (www.compsny.com) a New York real estate data firm, wanted to present detailed maps and high resolution imagery of all of Miami-Dade County, Florida, to its clients, in an easy-to-use Web format. Getting the raw data was simple; the county made it available at a nominal price to anyone…on more than 40 CD ROMs! The CDs contained detailed aerial photography broken into hundreds of individual “tiles” covering the entire Miami-Dade area. Usually, serving such a massive amount of data over the Internet would require a variety of expensive and complex software packages, but ComCarto developed a new approach using simple, inexpensive, and easily customized software produced by its partners, TatukGIS (www.tatukgis.com) and AtoZed (atozedsoftware.com).

The Application

   COMPS wanted a website where users could quickly view any tax parcel in the county, see lot dimensions, and view the 1-foot pixel aerial photography available for the county. Figures 1 and 2 show the extent of the database, and the way a particular lot appears to a user in the final Web browser interface. The user can turn the imagery on or off, toggle the dimensions and lot numbers on and off, pan about the map, and zoom in or out as desired. Figure 3 shows a lot with the dimensions and lot ID# turned on, and the aerial imagery turned off. The browser controls were kept very simple, and they are focused on the tasks that COMPS customers will want. Other controls would simply be a distraction, and were eliminated. Most important, the response of the site is very fast. The philosophy of Web serving used here assumes that users do not have fast connections, would balk at Java plug-ins, and do not want to download anything. Whether the user has Internet access via DSL, cable, or a dial-up modem, the transmission speed is very high because only a small, compressed image is being sent from the central server. Moreover, the vast amount of parcel data and aerial imagery have been compressed into a fraction of their original size, and loaded into a relational database that can locate any particular lot and its imagery with lightening speed. Most organizations that serve this sort of data rely on Oracle, or some other expensive and complex database, in addition to costly “middleware,” but ComCarto is doing it with simple Microsoft Access databases.

Behind the Scenes

   Figure 4 diagrams how the ComCarto application is constructed. The more than 35 gigabytes of high-resolution imagery were compressed to approximately five gigabytes of data in Access database files, in the TatukGIS PixelStore format. The graphic user interface (GUI), what the user actually sees in the Web browser, was developed using TatukGIS objects in a Borland-Delphi environment. The use of AtoZed’s IntraWeb software, which is supported by Delphi and Tatuk, meant that virtually no additional programming was required to move the application to the Web. This brings a tremendous savings in development time and serving costs, and it promotes wonderful synergy among the development staff we have, who are trained in programming in Delphi, but may not know how to do HTML, ASP, ArcIMS, etc. Before we began using these tools, it was necessary to have several people involved, each of whom was well-versed in a particular software brand and programming language. In the end, we would have to fit all these different pieces together. This extreme inefficiency and extra overhead are no longer required, because the same programmers using the same tools they employ to create fast desktop applications can work to create applications on the Web. Moreover, the tools involved are now limited and uniform: we do all development work in Borland-Delphi, using TatukGIS objects. Any database at all, Oracle, SQL Server, Access, etc. is compatible, and all map files are standard shapefile format.

   ComCarto does not serve these data from its own offices because COMPS, Inc. wanted to ensure that its staff would maintain the service. An additional advantage of our approach is that it was only necessary to email to COMPS a small application file, in order for its staff to load the application on its own server. (TatukGIS does require the purchase of an Internet deployment license for each server.) We have found that installation and portability problems are minimal with this software configuration, and providing software updates to clients is a simple as emailing them a new file.

The Power of the Web

   As GIS becomes more visible on the Web, imagery, highly detailed imagery, is often the first data layer required. The Tatuk PixelStore format provides a way to serve massive amounts of imagery from a compact and very low-cost base. MrSID imagery (from LizardTech) is another format that is very popular for serving aerial photographs over the Web, but until recently, developers had to purchase an additional software license to use this format with Tatuk applications: this is no longer true. Users with access to MrSID imagery archives (frequently the format of choice of the public sector) can now serve them over the Web via Tatuk applications without incurring an additional cost.

   With more and more counties and municipalities providing excellent base data at a nominal cost, the competitive pressure for quick, cost-effective, and flexible applications to serve the data over the Web will increase. These data sets are often massive—ComCarto serves a tax parcel map of New York City, nearly one million lots, over the Web—and the associated imagery regularly consumes gigabytes of storage. The approach that ComCarto has taken with Miami-Dade can be easily replicated to any area of the country where the data is available. In fact, we are currently reproducing this effort with a similar site for COMPS, Inc. for the West Palm Beach, Florida area, at a great savings in cost. The benefits to users are tremendous—they can see property lines, accurate, up-to-date aerial imagery, dimensions, and associated assessment data at a single site. The provider can password protect this information, and use a variety of subscription-access plans to allow customers to pay for only the data they need to view.

   This approach to serving data requires staff with some sophisticated programming skills. Still, managers should consider the fact that using off-the-shelf software will incur higher licensing and maintenance costs, but also will also require staff highly trained in a proprietary software to achieve comparable performance. And, the staff skills will not be transferable to any other application. This is a hidden cost of the “brand-name” approach to spatial data management. Flexibility can be its own reward.

About the Author

   Gary Ostroff has degrees from Princeton University, the City College of NY, and Hunter College, NY, and is a registered professional engineer. He has been developing GIS applications for natural resource protection and urban asset management for fifteen years. Gary can be reached at [email protected].

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