Imagery | Terrain Data

CHARLES COUNTY, MD

Description
Spatial Systems Associates, Inc. has performed a wide variety of GIS support functions for various agencies of the Charles County government since 1998. We started with acquisition of digital orthophotography and the development of a street centerline file, attributed with address ranges, for use by the E911 response group. This effort required an update from the digital orthophotography to the County's building planimetric data, which SSA accomplished. Property points attributed with the proper address were then placed within each building, and a street centerline file was generated with each segment attributed with the appropriate address range. The data was then provided to the County's E911 office for use in their dispatch operations. Following this effort, SSA acquired LiDAR data for the county. SSA's responsibility was to insure that the LiDAR acquisition contractor's workproduct conformed to the County's specifications and to FEMA quality requirements. The workproduct provided back to the County included first returns, last returns, bare earth mass points, and a Digital Elevation Model (DEM). From these workproducts SSA then developed Countywide 2-foot contours that conformed to national map accuracy standards. Upon completion of this work, we were selected by the Department of Utilities to design and build a GIS-based information system for the county's water and sewer infrastructure.

The Department of Utilities recognized the need to move to a digital data layer of its wastewater system maintenance and analytical functions—all of its operations were based on the use of deteriorating paper as-built drawings (and scanned versions of these) and the manual extraction of data as needed.

The Department approached SSA for assistance in early 2007, and SSA responded with a phased approach to build GIS datasets that could be fully integrated into the Department's evolving business methodology, using the available orthophotography. SSA built a map book and web application to locate plan drawing sets in the approximate area of the County represented on the drawings, pending the creation of a digital wastewater feature layer. SSA has scanned over 15,000 plan drawings at 400dpi grayscale for use in the vectorization task, and built a document indexing system that made the new scans immediately available to county staff via a web-based interface, which meant that field staff could now access the complete library of as-builts in the field utilizing ruggedized laptop computers equipped with suitable communications ability.

SSA then customized a geodatabase design for a pilot vectorization task for the Mattawoman Interceptor project (which links to WSSC facilities). The pilot vectorization was completed successfully and the Department contracted with SSA for the completion of the vectorization of the entire wastewater collection system. The conversion effort has included georeferencing of appropriate scanned images, vectorization of both water and sewer features, attribution of the resulting features with information on size, material, date of installation, and other information gleaned from the as-built drawings. In addition, SSA "associated" the raster images with relevant vector features so that, by selecting any particular feature, county staff could identify and view all as-built drawings on which that feature is depicted. Further, a print capability was provided that allows county staff to print all or a portion of the image to a hardcopy device should that be necessary.

As part of the conversion project SSA built a project tracking web site which gave the Department real time access to vectorization work product as it was posted to the site, and it provided a mechanism for resolving questions about system features and locations as they arose. The project tracking site had the added benefit of providing an audit trail of issues and resolutions posted over the life of the project. The department is now using the Esri-based project tracking web site as the basis for a system management application designed to be used by field crews to view system drawings and update feature information.

Along with development of these datasets, SSA has been providing ongoing consulting services to the County in its efforts to implement web-based GIS services. SSA has configured an ArcGIS Server and ArcSDE instance for Charles County, and is assisting the County in standing up and supporting web-based GIS functionality.

Additional services to Charles County have included development of sewershed boundaries following the development of the sewer vector data, and GIS support of the I&I studies that the County conducted with regional engineering support.

Our services to Charles County are continuing with assistance in the County's stormwater information system, assistance to regional municipalities, and coordination between the County and those municipalities as appropriate.