Maryland Creates Electronic Atlas to Make GIS Data Available
Maryland develops an electronic atlas of its GIS layers to solve data access problems.
By Kevin P. Corbley

Data access. It's a concern of virtually every organization that operates a GIS. And the issue is especially difficult at state and local government levels where GIS managers are caught in a conflict between mandates to make data widely available and the need to keep control over valuable information.
     Numerous local government offices have experienced the downside of finding out how popular their GIS really is. One department spends extensive time and resources developing the system and then hardly gets to use it because of the onslaught of requests from other agencies and offices for queries and searches.
     "We've had occasions where lawyers from the State Attorney General's Office drop by our office on their way to court to ask for a map or satellite image of a specific street intersection to use as evidence in a case," said Bill Burgess, director of the Geographic Information Services Division at the Maryland Department of Natural Resources (DNR) in Annapolis.
     The Geographic Information Services Division usually obliges any requests its GIS can handle, but at the expense of time that otherwise would be spent on building the system to support activities for which the DNR database was originally created - environmental permit review and natural resources planning and management.
     To field all of the requests, both internal and external, Maryland has developed an electronic atlas of its GIS data layers. Known as MERLIN (Maryland's Environmental Resources and Land Information Network), the on-line system brings maps, satellite images, aerial photos, thematic vector overlays, attribute files and data spreadsheets for the entire state directly to the desktop computers of DNR employees.
     Maryland sees the electronic atlas as a perfect answer to the GIS access problem because it makes data available without relinquishing control of it. At the front end of MERLIN is TNTatlas, a free viewing software package developed by MicroImages Inc. of Lincoln, Neb. It enables the user to access and display GIS layers and their attribute files, overlay data layers, make measurements and change map projections without altering the data in any way.
     Inside DNR where the data have been available for several years, MERLIN gets rave reviews. The department's Environmental Review Unit can examine construction and development permits to find potential natural resource impacts much more quickly now that all of its reference maps and databases are under a single user interface in digital formats. And MERLIN's benefits are becoming well known outside DNR as well.
     "Sometimes developers and county agencies send us proposed site plans before they even prepare their permits so we can alert them to potential permitting considerations in advance," said Ray Dintaman, director of the Environmental Review Unit.
     DNR is well aware that MERLIN's benefits extend beyond its own department. For this reason, Maryland is providing system access to other state agencies. But perhaps more importantly, the state is also taking another giant step forward with data access, offering MERLIN data sets to the public on compact disks at minimal cost.
     "We see GIS as a valuable tool for many private sector industries, and we want to introduce them to it by putting data in their hands," said Burgess. "We expect MERLIN's data to be used by real estate developers, banks, engineering consulting firms and environmental advocacy groups."
     Although getting MERLIN ready for public access has been time consuming, DNR expects it will pay off in the long run. The department envisions private consulting companies, working on behalf of developers, performing much of the site assessment work now done by state permit review personnel. This proactive approach to managing development will shorten permit approval times, help ensure that growth is directed to proper areas and protect valuable natural resource areas.

MERLIN Finds Potential Tower Sites
DNR personnel have been accessing data through the MERLIN system for several years, and for the last 18 months the Geographic Information Services Division has worked with public and private sector users to run the system through its paces at the department's headquarters in Annapolis.
     Diana Reynolds, an engineering consultant with R&D Associates of Burlington, Vermont, was offered the opportunity to use MERLIN on a water tower siting project for the city of Annapolis. The goal of the project was to suggest suitable locations for a planned water tower.
     "We used MERLIN to find optimal locations based on a number of cost, ownership, land use and environmental concerns," said Reynolds.
     The system is organized hierarchically, and the TNTatlas software is equipped with a HyperIndex tool that links data layers and attributes according to geographic location. This enables the user to navigate through data layers vertically from large-scale orthophotos to a small-scale Landsat image. Or the user can traverse horizontally from one map sheet to another in the same scale.
     For the first pass in the siting project, Reynolds and Burgess viewed an orthophoto of Annapolis. They scrolled through the photo looking for cleared land at least one-acre in size and preferably on city-owned property, such as schools. This would eliminate the cost of a land purchase. These parameters were easy to analyze in the system.
     A topographic layer was used to pinpoint areas 20 feet or more above sea level, a requirement for the tower to maintain the proper pressure in the water system. Steep slopes were also eliminated from consideration because they are difficult to build on. The first pass took about two hours.
     "It would have taken a couple of weeks to perform this part of the search, driving around town with a map book looking for open spaces," said Reynolds.
     The electronic atlas saved considerably more time in the second phase of the analysis. Once several sites were chosen, Burgess began overlaying thematic vectors critical to the screening process:
- National Wetlands Inventory Maps
- Sensitive Species Project Review Areas
- FEMA 100-year Floodplain
- Known Archaeological Site Grids
- National Register and State Historic Sites
- Historic Preservation Easements
- Protected Lands
     "We would have had to go to several state agencies to pull the necessary maps and find out if any of these sensitive areas overlapped with our first round of candidate sites," said Reynolds.
     Avoiding any kind of environmentally or historically sensitive area was a key consideration to the overall cost of the project. Not only does construction on these sites require preparation of various types of impact statements and special permits, but it can also place severe restrictions on the building process itself. The city of Annapolis, like a lot of private developers, wanted to avoid these costly issues.
     Based on the land-use and environmental sensitivity parameters, Reynolds used MERLIN to pinpoint 18 potential sites for the new water tower. In the third and final pass, Burgess pulled up a parcel layer called MdProperty View, which is produced by the Office of Planning. It contains zoning, ownership - and most importantly - information on appraised property values. With these financial concerns taken into account, the parcel information helped reduce the number of final candidate sites to eight.
     "MERLIN saved us several weeks of work," said Reynolds. She predicts home buyers will soon be accessing the easy-to-use system to assist them in searching for neighborhoods they like and houses they can afford.

Setting Up MERLIN
DNR has configured MERLIN as a client/server network operating on a Windows NT Advanced Server system. All data is stored on a series of five Pentium computer servers in DNR headquarters with the software running on a Pentium Pro. Any Windows, Windows NT, Windows 95 or Macintosh computer can access the servers across the DNR network.
     Although much of the data is spatial - maps, images, and vectors - the system also contains a wealth of attribute data, including demographic, street, parcel, wildlife and other information which is stored in tabular formats in database and spreadsheet files. DNR has linked the attributes geographically to the spatial data layers with TNTmips, the GIS and image processing software it uses for building and maintaining MERLIN.
     The department is testing wide-area network options so that field offices around Annapolis and throughout the state can access the system. Currently, only DNR employees within the departmental headquarters building can access it directly.
     Soon, the general public and other state personnel will access the system indirectly, on compact disks. The original MERLIN public access strategy called for establishing a wide-area network the public could dial directly into and retrieve data layers via 56 kilobyte lines. However, the state has since realized the data files are simply too large for these lines to handle. A higher volume line has been ruled out for the time being due to financial consideration.
     DNR will instead adopt CD technology to distribute MERLIN data sets. And it is making it easy for customers to use the data by imbedding TNTatlas software on every CD.
     "With the free atlas software right on the CD, customers won't need anything but a UNIX, IBM or Macintosh computer with a CD drive to access the data," said Burgess.
     Customers will be able to order the CDs by calling DNR or its authorized resellers and specifying their area of interest. For ease of distribution, the CD datasets will be packaged by U.S. Geological Survey 7.5-minute quadrangles. Each CD will contain all of the images, maps, vectors and attributes related to that quad. Prices for the CDs may start as low as $100 per quad, with the first CDs shipped next year.
     In addition to DNR's own data, MERLIN contains a variety of data from the Maryland Office of Planning, State Highway Administration, Department of Housing and Community Development, research institutes and a variety of federal agencies. DNR will make royalty payments to some of these agencies for the use of their data.

MERLIN for Experienced Users
Many potential MERLIN customers are accomplished GIS users. For them, Governor Parris N. Glendening has directed creation of the 'Technology Toolbox' as part of his Environmental Agenda.
     The Toolbox program offers coordinated data distribution from several state agencies and their authorized resellers. Most state data are available in county-size files, but with no viewing software imbedded with the datasets. This data product is designed for customers to load directly into their existing system for use with any popular GIS software, or low-cost viewing packages being written by some data resellers.
      "MERLIN embodies the cooperative spirit of Maryland state agencies," Governor Glendening said. "Years of coordinating our efforts have provided substantial returns through integrated systems like MERLIN, that allow state employees and the public to work smarter, faster and more cost effectively."

About the Author:
Kevin Corbley is a freelance writer and consultant specializing in remote sensing, GIS and GPS. He is located in Denver, Colo., and may be reached at 303-987-3979 or by e-mail at [email protected]

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