Name: 1ft Elevation Contours - NAVD88

Display Field: CONTOUR

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Description: <DIV STYLE="text-align:Left;"><DIV><DIV><P><SPAN>Product: Contour data for Fairfax County, Virginia as part of the required deliverables for the 2022 VA NorthernVA 1 B22 project administered by the U.S. Geological Survey.</SPAN></P><P><SPAN /></P><P><SPAN>Project description: Class 2 (Ground) lidar points in conjunction with the hydro breaklines were used to create a 1-foot hydro-flattened Raster DEM. Geographic Extent: Alexandria, Arlington, Fairfax, Falls Church, Loudoun, Manassas, Manassas Park, and Prince William counties Virginia, covering approximately 1351 square miles. Dataset Description: The lidar project called for the Planning, Acquisition, processing and derivative products of lidar data to be collected at a nominal pulse spacing (NPS) of 0.35 meters. Project specifications are based on the U.S. Geological Survey National Geospatial Program Base Lidar Specification 2022, Revision A. The data was developed based on a horizontal projection/datum of NAD83(2011), State Plane Virginia North, Feet and vertical datum of NAVD88 (GEOID18), Feet. Lidar data was delivered as processed Classified LAS 1.4 files, formatted to 4404 individual 3000 ft x 3000 ft tiles clipped to the DPA, as tiled intensity images, as tiled bare-earth DEMs, as tiled all-return MSHRs; all tiled to the same 3000 ft x 3000 ft schema. Ground Conditions: Lidar was collected in late 2022, while no snow was on the ground and rivers were at or below normal levels. In order to post process the lidar data to meet task order specifications and meet ASPRS vertical accuracy guidelines, Sanborn Map Company, Inc., established a total of 16 ground control points that were used to calibrate the lidar to known ground locations established throughout the project area. An additional 84 independent accuracy check points, 47 in Bare Earth and Urban landcovers (47 NVA points), 37 in Tall Grass and Brushland/Low Trees categories (37 VVA points), were used to assess the vertical accuracy of the data. These check points were not used to calibrate or post process the data.</SPAN></P><P><SPAN>Contact: </SPAN><SPAN STYLE="font-size:14pt"><SPAN>Fairfax County Department of Information Technology GIS Division</SPAN></SPAN></P><P><SPAN>Data Accessibility: Publicly Available</SPAN></P><P><SPAN>Update frequency: Never</SPAN></P><P><SPAN>Last Revision Date: 1/28/2025</SPAN></P><P><SPAN>Creation Date: 1/28/2025</SPAN></P><P><SPAN>Feature Dataset Name: DIT_GIS.GISMGR.TOPOGRAPHIC</SPAN></P><P><SPAN>Layer Name: GISMGR.CONTOURS_1FT_NAVD88</SPAN></P></DIV></DIV></DIV>

Copyright Text: Fairfax County, Virginia; Fairfax County Department of Information Technology GIS Division; U.S. Geological Survey, Sanborn Map Company, Inc.

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Fields:

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• CONTOUR ( type: esriFieldTypeDouble, alias: Elevation in Feet )
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