Delaware Valley Regional Planning Commission
Geographic Extent: Delaware Valley, covering approximately 3260 square miles over the Philadelphia Metro area, comprised of of 8 contiguous counties located in the states of Pennsylvania and New Jersey. Delaware Valley 2015 LiDAR project called for the Planning, Acquisition, processing and derivative products of LIDAR data to be collected at a nominal pulse spacing (NPS) of 0.7 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 UTM Zone 18, NAD83 (2011), meters and vertical datum of NAVD1988 (GEOID12A), meters. LiDAR data was delivered in RAW flight line swath format, processed to create Classified LAS 1.4 Files formatted to 25 individual 1500 meter X 1500 meter tiles for the pilot (3752 individual 1500 meter X 1500 meter tiles for the entire project area), Bare Earth DEMs tiled to the same 1500 meter X 1500 meter tile schema, and Breaklines in Esri shapefile format. Ground Conditions: LiDAR was collected in spring of 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 76 calibration control points in order to calibrate the LIDAR to known ground locations established throughout the Delaware Valley project area. The accuracy of the data was checked with 91 NVA points and 70 VVA points (161 total QC checkpoints).
Purpose: Classified LAS files are used to show the manually reviewed bare earth surface. This allows the user to create Breaklines and Raster DEMs. The purpose of these lidar data was to produce high accuracy 3D hydro-flattened Digital Elevation Model (DEM) with a 1-meter cell size. These raw lidar point cloud data were used to create classified lidar LAS files, 3D breaklines, and hydro-flattened DEMs as necessary.
Pennsylvania Spatial Data Access (PASDA)
Delaware Valley Regional Planning Commission (DVRPC)
Lidar data were acquired and calibrated by Quantum Spatial. All follow-on processing was completed by the prime contractor.
Horizontal Positional Accuracy
Please see the Accuracy Analyst report for a detailed report showing the 57 control points measured to produce the NSSDA value of 0.737 meters.
Vertical Positional Accuracy
The specifications require that only raw Nonvegetated Vertical Accuracy (NVA) be computed for raw lidar point cloud swath files. The raw NVA was tested with 91 independent survey points distributed throughout the project area and located in open terrain. These checkpoints were not used in the calibration or post-processing of the lidar point cloud data. Specifications for this project require that the raw NVA be 19.6 cm or better AccuracyZ at 95 percent confidence level.
The specifications require that Nonvegetated Vertical Accuracy (NVA) be computed for DEM files. The NVA was tested with 91 independent survey points distributed throughout the project area and located in open terrain. These checkpoints were not used in the calibration or post-processing of the lidar point cloud data. Specifications for this project require that the NVA be 19.6 cm or better AccuracyZ at 95 percent confidence level.
The specifications require that Vegetated Vertical Accuracy (VVA) be computed for DEM files. The VVA was tested with 70 independent survey points distributed throughout the project area and located in vegetated terrain. These checkpoints were not used in the calibration or post-processing of the lidar point cloud data. Specifications for this project require that the VVA be 29.4 cm or better at the 95th percentile.
None. However, users should be aware that temporal changes may have occurred since this data set was collected and that some parts of this data may no longer represent actual surface conditions. Users should not use this data for critical applications without a full awareness of its limitations. Acknowledgment of the U.S. Geological Survey would be appreciated for products derived from these data.
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