| Description | Spatial | Attributes |
Location of all buildings throughout Prince George's County, Maryland
The countywide building roofprint information was stereo-photogrametrically captured and compiled at a 1 inch=200 feet scale using geodetic control and 1:14,400 scale aerial photography taken in April, 1993. The building layer will be stereo-photogrametrically captured from digital orthophotography. The term commonly used for this planimetric layer is building footprints. In actuality, the true building footprint cannot be gleaned from aerial photography and so the capture of buildings is more or less confined to the capture of rooflines. All structures with roofs having an areal coverage of 200 square feet or greater will be captured from the photography. Buildings will be delineated by tracing the apparent edge of the roofline for dwellings, businesses, houses, house trailers, garages, and barns. Where appropriate, buildings will be squared at the corners so that the corners are orthogonal and within the established mapping accuracy tolerance for 1:2400 scale mapping. Interior rooflines, such as dormers, will not be captured. Roofline extensions, such as carports, decks, patios, stairs, etc. will not be captured or shown. The building layer should be a seamless cover with no buildings being split for some imposed sheet tiling. Those buildings found at the edge of the model (at the Prince George's/Montgomery County boundary or the Prince George's/Washington D. C. boundary) should be shown in their entirety. All building polygons should show proper closure and contain one pseudonode. The vectorized building roofline should very closely fit the building rooflines displayed on the digital orthophotography. All building coverages will be processed through the QC AML's (Arc Macro Language) developed by Maxima. These AML's test for the presence of appropriate subdirectories that are created by ARC/INFO (i.e., .pat, .aat, .nat, etc.), give a description of the coverage, test for tic and bnd agreement with the master grid, check for labelerrors, and describe feature coding and annotation present in the building layer. The coverage is then visually checked for building addition or deletion by overlaying the building coverage on the appropriate digital orthophoto tile. Errors are reported on hard copy composite planimetric plots that are available for each tile layer. Results of this QC effort are maintained by the GIS coordinator in a series of three ring binders. All data tiles are checked in this fashion. The resulting coverages are 100% accurate for buildings that met the criteria for capture as of the date of the aerial photography April 1993.