Breaklines

The Virginia Base Mapping project encompasses the entire land area of the Commonwealth of Virginia over 4 years. The State boundary is buffered by 1000'. Coastal areas of the State bordering the Atlantic Ocean or the Chesapeake Bay are buffered by 1000' or the extent of man-made features extending from shore.

This metadata record describes the generation of new Digital Terrain Model (DTM) and contours generated at 2-foot intervals. All products are being delivered in the North American Datum of 1983 (1986), State Plane Virginia North. The vertical datum was the North American Vertical Datum of 1988 (NAVD88) using GEOID12B.

The collection of aerial photography and production of an ortho quality DEM and orthophotography was executed to capture the existing ground conditions at a specific point in time for the purpose of GIS analysis. Orthophotography along with DEM data typically provides an accurate base for digitally representing geographic features upon which a GIS is built. The Virginia Geographic Information Network Division (VGIN) is the lead public agency in the Commonwealth for spatial data and GIS.

VGIN's mission is to facilitate the cost-effective development and use of spatial data, GIS, and related technologies in organizations throughout the Commonwealth. Quantico Marine Corp Base (QMCB) area within Prince William County was excluded from 2017 Contour project. This area digital imagery was flown at 12 inch pixel resolution.

The remainder of Prince William County was captured at a 6-inch resolution. The Contour and other associated data was created utilizing the 6-inch resolution. A Breakline is a line used to connect data representing a distinct surface feature, like a ridge line, edge of pavement, toe of a slope, centreline of a road, or flowline of a ditch or stream.

A breakline is a linear feature that describes a change in the smoothness or continuity of a surface.