Description: This data set is one component of a digital terrain model (DTM) for St. Johns County. The dataset is comprised of mass points, 2-D and 3-D breakline features, 1-foot and 2-foot contours, ground control, vertical test points, and a footprint of the data set, in the ESRI ArcGIS File Geodatabase format. In accordance with the counties specifications, the following breakline features are contained within the database: closed water bodies (lakes, reservoirs, etc) as 3-D polygons; linear hydrographic features (streams, shorelines, canals, swales, embankments, etc) as 3-D breaklines; coastal shorelines as 3-D linear features; edge of pavement road features as 3-D breaklines; soft features (ridges, valleys, etc.) as 3-D breaklines; island features as 3-D polygons; concretedam, culvert, footprint, lowconfidence, lowconfidenceanno, overpass, pipe, roadcenterlineoverbridge and swamppoint as 2-D features. Contours were generated from LiDAR ground class and breaklines and meet National Map Accuracy Standards. The LiDAR masspoints are delivered in the LAS file format based on the Florida statewide 5,000' by 5,000' grid. Breakline features were captured to develop a hydrologically correct DTM. The GEOID model used to reduce satellite derived elevations to orthometric height is GEOID12A. The coastalshoreline has a constant value of -0.6’ that was statistically derived from the LiDAR point cloud collected within the 2-hour window of MLL tide. 2008 Hydrographic and soft features were used to supplement the 2013 breaklines in Low Confidence areas.
Copyright Text: Data content is created and/or maintained by the St. Johns County GIS Division and Woolpert, Inc.