More MetadataBuilding Footprints are a base map data layer derived by automated processes and processed for cartographic representation at 1:2400 scale. The polygon features represent the outlines of buildings and structures as seen from above and are mapped to National Map Accuracy Standards (NMAS). Purpose: Building footprints are used as reference points in the parcel mapping process and in address assignment. They are also used in the provision of emergency services. Supplemental Information: OMAGI updates all base map data via a photogrammetric process, using aerial imagery that is flown yearly in phases. A different portion of the County is updated each year with the base map maintenance services contract, depending upon development patterns and update funding. See "Lineage" section, in the full FGDC version, for the list of extents for each Phase area, which are listed as Data Sources. For a map of the most recent reviews and updates within the county, pleaseclick here. Data are stored in the corporate ArcSDE Geodatabase as a polygon feature class. The coordinate system is Virginia State Plane (North), Zone 4501, datum NAD83 HARN, US Survey foot units. Use Constraints: Every reasonable effort has been made to assure the accuracy of these data. Loudoun County, Virginia does not assume any liability arising from the use of these data. These data are provided without warranty of any kind, expressed or implied, including, but not limited to, the implied warranties of merchantability and fitness for a particular service. Reliance on these data is at the risk of the user. These data are intended for use at 1:2400 scale or smaller. Maintenance and Update Frequency: Annually Completeness Report: Base Map features have been updated from different sources and in different years. Although the entire county was originally mapped, users should be cautious and aware that any particular area of interest may not be absolutely current and up to date. This is a result of the development patterns and update funding determining what area to update, with the entire County being reviewed prior to any update. Data Owner: Office of Mapping and Geographic Information