| Maryland Makes GIS Data Available on the Web
By Kevin P. Corbley When it comes to making GIS data available both inside and outside the enterprise, Maryland leads every other state in the country. In just over two years, the state's Department of Natural Resources (DNR) has progressed from dishing out land information on CDs, to serving it up on the Internet.
"Putting information on the Web is a natural progression of GIS development," said Bill Burgess, GIS Division Program Manager at Maryland DNR. "We have found it is better for us to give access to other agencies and the public because it takes a burden off our staff."
DNR originally built the GIS for environmental permit reviews and natural resource planning but, as data from other state agencies came pouring in, so did outside requests for information. To handle the onslaught, DNR used TNTatlas - a free software tool from MicroImages Inc. of Lincoln, Neb. - to create an electronic atlas of GIS data layers.
The atlas became known as MERLIN, for Maryland's Environmental Resources and Land Information Network, and includes maps, satellite images, aerial photos, and thematic vector overlays relating to each of the state's 23 counties. TNTatlas contains a HyperIndex tool and allows developers to link spatial data with attribute files and spreadsheets so users can access maps and database information together.
Access to MERLIN was first offered to DNR personnel on stand-alone computers, and then through an Ethernet local area network. MERLIN's datasets were offered to the public on CDs that were occasionally combined with TNTatlas software. At the time, Maryland considered MERLIN the ideal means of making GIS data available without giving unbridled access to the GIS itself. (See EOM, Dec. 1997, pp. 14-17.)
Just as the CDs went into distribution in mid-1997, the concept of publishing GIS data on the Web was gaining popularity. Maryland DNR saw the Internet as a more practical alternative for widespread data access than were the CDs. However, DNR GIS staff members were reluctant to abandon this simple interface to dozens of data layers already organized within TNTatlas. They contacted MicroImages for a solution.
At about the same time, MicroImages was studying various Web options for its TNTatlas, TNTmips, and other software products, and it welcomed Maryland's input. Ultimately, MicroImages created TNTserver, a tool for providing rapid access and viewing of large volumes of geographic data via the Web.
In keeping with the design philosophy of other TNT products, TNTserver was developed to serve raster, vector, CAD, and other layers in multiple formats. Moreover, the server was designed to access graphical or tabular data either from an internal TNT relational database management system, or via other external databases such as Access, Oracle, and DB2. Users access the system over the Internet, or via an intranet.
"It's important to distinguish TNTserver from an online GIS," said MicroImages president Lee Miller. "TNTserver is a map- and image server, which protects the data from being altered or downloaded as might occur with an online GIS."
This built-in safeguard for data access fulfilled Maryland's objective to make its data available on a view-only basis. In fact, this design feature gave SPOT Image Corp. sufficient confidence to allow DNR to use full-resolution SPOT satellite imagery during a one-year test period of a MERLIN basemap, which would have violated the company's standard-use agreement if the data were to have been downloaded.
MERLIN went online at www.mdmerlin.net in July, and the site was upgraded and enhanced for an official unveiling at the Maryland Technology Showcase in December 1999. The system was personally demonstrated to 1200 people at the Showcase, and it has been used extensively ever since. Building MERLIN Online
At last count, MERLIN totaled 80 gigabytes - compressed from 150 gigabytes - and contained 70 layers of data covering the entire state. Primary data layers include: thematic maps showing locations of wetlands; protected lands; sensitive areas; historic sites; watersheds; soil types; political entities; and land use. SPOT 10-meter panchromatic satellite imagery, USGS 7.5' quad maps, and 3.75' color-infrared digital orthophotos with one-meter resolution, serve as the base maps upon which thematic layers are displayed.
The primary data sets were supplied by Maryland DNR, the Department of Housing and Community Development, the Office of State Planning, and the State Highway Administration. The SPOT imagery and orthophotos were purchased from SPOT Image Corp. and VARGIS LLC, respectively.
DNR soon hopes to add new color orthophotos produced by county agencies at one-foot resolution. MERLIN could quickly swell to 250 layers and one terabyte, which is no problem for DNR since both the server and client are fully scaleable. System performance is not affected by overall database size.
"Other states have orthophotos or various maps on Internet sites, but I am not aware of any that has its entire state online with this variety of data," said Burgess.
DNR installed TNTserver on a Hewlett Packard server with four 550Mhz Pentium XEON processors. It is connected to a 100MHz Ethernet LAN that accesses the HyperIndex stacks in TNTatlas residing in three separate RAID file servers.
MERLIN users access the system online with Internet Explorer 5.0 or Netscape Navigator 4.6. When a user connects to MERLIN, a TNTclient program, or Java 1 applet, is sent to their machine. This allows them to browse and query the various data layers. Maps, images, orthophotos and other data are pyramided, tiled, and compressed for extremely rapid display.
"All of the same TNTatlas functionality found in earlier versions of MERLIN are retained in the online system," said Burgess. "Images are displayed as JPEGs." Tapping MERLIN's Magic
MERLIN users are first presented with a Landsat overview of the entire state, with county outlines visible, or else they can choose a county directly from a text list. On the left side of the screen, a list of data layers offers many alternatives of thematic map and boundary overlays. The user can zoom in for successively greater detail, first to the 10-meter SPOT image and then down to the 7.5' quad sheet and even a 3.75' orthophoto view for most areas. At that level, individual houses are visible.
From any screen, the user can navigate around the display and zoom in or pan out on areas of interest, moving across images or jumping back and forth from images to maps to photos. Searches for particular properties can be conducted by dragging the mouse pointer around the image. The system gives coordinates for any point on the screen. Additionally, the mouse can be used to click between two areas, or to draw a polygon for the system to calculate distances and areas in English or Metric units of measurements.
The value of MERLIN is clearly illustrated by the data layers that the user displays on the image or photo, done simply by clicking from the onscreen Layer Control list. All views are prepared live in response to user inputs, as opposed to merely serving up canned maps. Single or multiple layers, such as protected habitats or historic sites, can be overlaid to create custom thematic maps. Even if different map projections are used, the server reconciles and scales the view as required.
For any data layer, the user can click on the list to call up metadata files. These files tell how that particular data was acquired, its date of collection, its scale, and who collected it.
DNR plans links to other URLs directly from MERLIN so users can get additional information from other web sites. For instance, a research group has approached DNR about creating a link between MERLIN's environmental data and the Global Legal Information Network (GLIN) at the Library of Congress. This link would forward a search string to allow direct retrieval of abstracts and full text for international and national laws relevant to that feature.
One of the main advantages of stacking data in the TNTatlas format is that a user - for example, a land developer - can zoom in on a specific site or property and learn everything about it, layer by layer. The developer can find out if wetlands, protected areas, historic sites, or other factors that could potentially impact development, exist there.
"The most interesting aspect of the server is a function called Info Tips," said Burgess. "We called it 'Bubba Proof' because anybody can use Info Tips to get information."
The idea behind Info Tips is simple. The user selects an area, such as a property, and then clicks one button. MERLIN searches every available data layer that has information related to that property, and then generates a list of critical information. For example, the list might tell whether the land was protected, sensitive, or contained historic elements. The election district, zoning category, flood plain status, and dozens of other facts are included in the list.
"With the click of a button, the user gets the information that everybody wants to know about a site or property," said Burgess. Benefiting from MERLIN
Ken Miller, Maryland DNR's chief of Spatial Data Production Services, says that having MERLIN online instead of on CDs has benefits for several user groups. First, of course, is the DNR staff, which can now access up-to-date information from any office around the state. Next are the many environmental groups with whom the DNR routinely works, such as the Chesapeake Bay Foundation and the Save Our Streams Team. Previously, these groups had to submit information inquiries to DNR staffers, which consumed time for both parties.
Another MERLIN users group is educators and their students. During the MERLIN testing period, several schools had access to the system. Its geographic and environmental applications are obvious, but teachers have found other uses for this system as well.
"We can us it in math, science, social studies, and physical education," said Linda Zeigenfuss, a support technician at the Maryland Department of Education. "Our physical education students are designing runs with it. They measure distances and check out elevation changes to create running routes."
DNR is working hard to get the word out about MERLIN to the business and development community. The agency believes it will actually help bring new business to the state.
"Companies that are thinking of moving to Maryland, or relocating within the state, can use this system to search sites for red flags that might cause denial of a permit or delay in processing," said Burgess.
He added that MERLIN will give businesses a good feel for what they can expect from an upcoming permitting process relating to a new building or development. Ultimately, DNR hopes that businesses will have better experiences in their dealings with the state government.
"We are providing a tool that will help a business locate to a good site for their specific purposes - instead of merely finding the cheapest piece of land that meets access requirements - and then working their way through permitting problems they didn't expect," said Burgess. About the Author:
Kevin Corbley is the principal in Corbley Communications Inc., Littleton, Colo. He may be reached at 303-979-3232, or via e-mail at [email protected]. Back |
