Description: This feature class is a subset of a larger 2015 5ft topographical dataset that was created at SanGIS. This feature class covers the Alpine, Central Mountain, Jamul-Dulzura, Mountain Empire area approximately. The dataset was created by clipping the larger topographical dataset to the Mountain Empire cell of the SanGIS Topographical Index (GRID_2015_5Ft_Topo_Index layer).Geographic Extent: San Diego, California, covering approximately 1,617 square miles. Dataset Description: San Diego, California 2015 QL2 LiDAR project called for the planning and acquisition of LIDAR data to be collected at a nominal pulse spacing (NPS) of 0.7 meter. Project specifications are based on the U.S. Geological Survey National Geospatial Program Base LIDAR Specification, Version 1.2. The data was developed based on a horizontal projection/datum of NAD83 (2011) State Plane California VI, US survey feet and vertical datum of NAVD1988 (GEOID12B), US survey feet. LiDAR data was delivered in RAW flight line swath format, processed to create Classified LAS 1.4 Files formatted to 2,045 individual 2,500-foot x 2,500-foot tiles, corresponding 2.5-ft hydro-flattened bare-earth DEMs tiled to the same 2,500-foot x 2,500-foot schema in ERDAS .IMG format, and Breaklines in Esri file geodatabase format. These raw lidar point cloud data were used to create classified lidar LAS files, 3D breaklines, and hydro-flattened DEMs as necessary. This resulting data was used to create the raw, individual five foot contour tiles (SANDAG). SanGIS then merged all of the raw, individual five foot contour tiles (558 Nr). The feature class was then Dissolved by Contour (no multipart features, and "Unsplit lines" selected). The XY Tolerance was set at the default (0.00328083 ft), so some of the line segments that were closer than this tolerance snapped together and created an overhanging line segment. In order to get rid of these very small lines, any remaining individual lines less than 1" (0.08333 ft) were removed from the data using the shapelength field to select them. An INDEX field was added based on the following index values (5, 10, 20, 50, 100, 200 and 500) to facilitate easy filtering of the topo data to these elevation values. The Simplify Line tool was then run to reduce the number of nodes along the contour lines, to reduce file size and improve performance. A Simplification Tolerance of 0.25 feet was chosen as an optimal value upon testing, while retaining as much of the original line shape as possible, while significantly reducing the file size. The POINT_REMOVE Simplification Algorithm was used (default option). Ground Conditions: LiDAR was collected in late 2015, 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, Quantum Spatial established 39 calibration control points in order to calibrate the LIDAR to known ground locations established throughout the project area. The accuracy of the data was checked with 119 QC points.
Service Item Id: 3ea2a97eb8ce49819094b8c5fba33f87
Copyright Text: SanGIS, SANDAG, Strategic Alliance for Risk Reduction II(STARR II), Federal Emergency Management Agency (FEMA).
Quantum Spatial Company flew the LiDAR and processed the data.