| Maryland County Devises Efficient Conversion Procedure
By Kevin P. Corbley Residents of Anne Arundel County, Md., enjoy the best of both worlds. Many live in waterfront homes on Chesapeake Bay or one of its tributaries, and those who reside inland are seldom more than a few minutes from the water. And for work, county residents are located equidistant between Baltimore and Washington, D.C., each less than 45 minutes from the county seat in Annapolis.
The county's economy is booming as more people decide to spend a few extra minutes in commuter traffic so they can take advantage of the recreational and leisure activities of the bay during evenings and weekends. As a result, housing developments, business parks and shopping centers are being built at a record pace across the county.
As typically occurs in rapidly growing areas, keeping pace with development pushes the resources of local government offices to their limits. Such is the case in the Anne Arundel County Department of Public Works. The department is inundated with requests for property information from developers, homeowners, landscape architects and building engineers.
"We are fielding between 8000 and 9000 data requests per year in our office," said Wally Atkinson, director of the department's Technical Engineering, Drafting and Records Research Division. "We have to dedicate an extraordinary amount of staff time [to assist] people who want information."
Developers and engineers go to the division office in Annapolis to obtain details on water and sewer locations in areas where they are planning new buildings or homes. Citizens who visit the division usually want to find tax assessment information on their properties or ownership data for neighboring lots.
Currently, many of these inquiries are handled manually by sorting through a variety of paper records and mylar sheets in the division's file room. The person seeking the information can either view the hard copy there, or else purchase a printed copy for about $5. Each request involves the attention of a division staff member.
However, the division is now fine-tuning a GIS-based document and map viewing system called CountyView that will greatly increase the speed with which information requests are handled, thereby reducing staff administration time. Initially, CountyView will be accessible to the public at the division office, and eventually at computer kiosks in other county offices.
Although CountyView will soon remove a huge burden from the Technical Engineering, Drafting and Records Research Division, its development has added to the group's workload over the last two years. The division has been tasked with creating the utility basemap and populating data layers in the CountyView system.
To accomplish this without losing ground on other duties, the division has devised an efficient procedure for the partial conversion of pertinent utility data for inclusion in the system. The division performs the partial data conversion in Autodesk's AutoCAD program, with key assistance from integrated software tools from Hitachi Software Global Technology Ltd. (HSGT) of Westminster, Colo. Planning CountyView
Anne Arundel Public Works contracted GeoNorth Inc. of Anchorage, Alaska, to design and implement the CountyView system. GeoNorth specializes in creating applications with GIS products from ESRI Inc. of Redlands, Calif. CountyView incorporates ARC/INFO and MapObjects products for storage and display of geographic layers, while most tabular property and utility data will reside in native databases.
The Technical Engineering, Drafting and Records Research Division maintains numerous maps, images and databases that are being integrated into the new system. The division's archive contains about 60,000 drawings stored in the Records and Research Room of the Technical Engineering Building in Annapolis.
Important maps include aerial photographs, utility operating maps and as-built drawings. The operating maps show the locations of all water, sewer, and storm drain pipes. The as-builts are engineering drawings depicting the actual installation configuration of each pipe, valve, invert, and other utility feature.
In the design of CountyView, the division opted to use the operating maps as the basemap for the system because the utility data on those maps are the primary reference points for most information requests. The division also decided to divide all maps and data layers into tiles. Displaying the basemap in tiles requires much less memory capacity in the system. Preparing for CountyView
The division's first task was to scan the paper operating maps and drawings for inclusion in the digital system. After the maps were scanned in raster format, the technicians used a tool called Image Edit from HSGT for a crucial phase of its system development.
Image Edit runs inside AutoCAD and enables the technicians to georeference the raster files to the NAD 83 coordinate system, which was chosen as the standard for the system. The software contains a variety of rubbersheeting commands to position and scale the rasters correctly. All rasters are saved from Image Edit in world files which maintain the correct mathematical definitions of location coordinates.
"Georeferencing is probably the most important step in the [data preparation] process because it ensures that data in all 130 system layers will match up precisely to the basemap," said Kevin Langston, CAD manager and GIS specialist. "If the system shows a buried water pipe 30 feet from a house, that resident should be able to walk off 30 feet and find the pipe."
The tiling structure used in the system adds to the importance of georectification. Each pipe must be precisely located by geographic coordinates so that multiple sections of pipe will match and appear continuous as the viewer browses and moves the display from one tile to another.
After the operating maps are tiled and georeferenced, the technicians use Image Edit to clean up the rasters. They remove speckle from the digital drawings that may result from creases or blemishes on the originals. They can also erase and change any old symbols or text that do not conform to current standards.
In the next phase of data preparation, the division technicians utilize AutoCAD to digitize the raster drawings. However, there are simply too many operating maps to vectorize them in their entirety, so the technicians perform a partial vectorization. They take only the important utility data from the maps, leaving behind the topologic information in raster.
The division is keeping the CountyView basemap in raster format for the sake of practicality. The majority of operating maps that form the basemap have little or no information on them that requires vectorization. Therefore, the county saves time and money by maintaining those maps in raster.
"There is no need to vectorize 4000 operating map drawings when we really are only working with about 300 of them," said Langston.
The vectors are sent to a newly formed GIS Division which updates and codes each vector to its proper GIS layer. The coding process links all of the water, sewer and utility equipment with the as-built drawings and the databases. This makes it possible to click on a water meter, manhole cover or fire hydrant in CountyView and view graphical profiles of the pipes underneath, as well as the dimensions, installation date and other tabular data.
Once the vectors have been coded, they go back to the AutoCAD technicians who then re-rasterize them in Image Edit. By converting them back into rasters, the updated and coded vectors can be included once again into the raster basemap in CountyView to maintain the continuity of the background map.
Technicians compare symbology and text in the new and old rasters to make sure they are consistent. Changes are made directly in Image Edit.
While the division is converting this data, it must still keep up with the influx of new graphics generated for the construction of 30 or so new building projects every month. In many cases, these new as-built files are submitted as AutoCAD drawings with many hand-drawn corrections on them.
Technicians use another Hitachi software tool, called Image Tracer, to vectorize these hand-drawn corrections. This software automatically follows lines on the scanned drawing and converts them to AutoCAD polylines, circles and arcs. This automated procedure is much faster than vectorizing the drawings in AutoCAD. Making CountyView Available
Anne Arundel Public Works expects to make CountyView available to the public before the end of this year. Discussions are under way as to where additional access kiosks will be located. Early next year, the department will publish static maps from the system on its web site. Publishing CountyView live on the Web could occur later next year.
"We will make all of our public record files available through CountyView," said Langston.
Initial reaction to the system is extremely positive. Highest marks are given to its search capabilities, which allow a user to query property information by inputting an address, phone number, tax identification number, block and parcel identifier, or owner name. If none of that information is known, the user can browse on-screen through aerial photographs until the correct property is located.
When the desired property is found, the user can click on it to access the consolidated property file that contains information on ownership, tax assessments, water/sewer billing numbers, lot size, and parcel map. Such details are helpful to homeowners in comparing their tax assessment against comparable properties in order to challenge appraisal values.
Developers, civil engineers, and cable installers can click on any property to view the water, sewer, and storm drain pipes that connect to and run through the parcel. All relevant information can be called up from its database with the click of a mouse.
CountyView runs on an Oracle server and currently accesses six different databases. By the time it is fully operational, another six servers will be linked.
"Searching for property information in a digital system like this is much easier than thumbing through the file cabinet," said Langston. "This system will save time for us and for our customers in the county." About the Author:
Kevin Corbley is the principal in Corbley Communications in Denver, Colo. He may be reached at 303-979-3232, or at [email protected]. Back |
