2017 USGS Lidar: West Chesapeake Bay Watershed, VA

Product: These lidar data are processed Classified LAS 1.4 files, formatted to 6517 individual 1500 m x 1500 m tiles; used to create intensity images, 3D breaklines and hydro-flattened DEMs as necessary.

Geographic Extent: Virginia, covering approximately 5282 square miles.

Dataset Description: VA West Chesapeake Bay Watershed 2017 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 NAD83 (2011), Universal Transverse Mercator, meters and vertical datum of NAVD88 (GEOID12B), meters. Lidar data was delivered as processed Classified LAS 1.4 files, formatted to 6517 individual 1500 m x 1500 m tiles, as tiled Intensity Imagery, and as tiled bare earth DEMs; all tiled to the same 1500 m x 1500 m schema.

Ground Conditions: Lidar was collected from April 2017 to May 2018, 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, Dewberry established a total of 24 ground control points that were used to calibrate the lidar to known ground locations established throughout the VA West Chesapeake Bay Watershed project area. An additional 224 independent accuracy checkpoints, 128 in Bare Earth and Urban landcovers (128 NVA points), 96 in Tall Grass and Brushland/Low Trees categories (96 VVA points), were used to assess the vertical accuracy of the data. These checkpoints were not used to calibrate or post process the data.

Data were subsequently reprocessed to Entwine Point Tile (EPT) format in web mercator projection with vertical meters. The EPT form of the data is used by the NOAA Digital Coast Data Access Viewer, which this metadata record is supporting. Additional processing steps may have been done by the Data Access Viewer and will be recorded in the lineage section.

To acquire detailed surface elevation data for use in conservation planning, design, research, floodplain mapping, dam safety assessments and elevation modeling, etc. Classified LAS files are used to show the manually reviewed bare earth surface. This allows the user to create Intensity Images, Breaklines and Raster DEM. 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 lidar point cloud data were used to create intensity images, 3D breaklines, and hydro-flattened DEMs as necessary.

USGS Contract No. G16PC00020 CONTRACTOR: Dewberry Consultants,

LLC. SUBCONTRACTOR: Leading Edge Geomatics (LEG) and Axis Geospatial, LLC Lidar data were acquired and calibrated by Aerial Scanning Services. All follow-on processing was completed by the prime contractor.

The following are the USGS lidar fields in JSON:

{

"ldrinfo" : {

"ldrspec" : "U.S. Geological Survey (USGS) - National Geospatial Program (NGP) Lidar Base Specification v1.2",

"ldrsens" : "Riegl LMS-Q1560",

"ldrmaxnr" : "15",

"ldrnps" : "0.70",

"ldrdens" : "2",

"ldranps" : "0.70",

"ldradens" : "2",

"ldrfltht" : "2087",

"ldrfltsp" : "150",

"ldrscana" : "58.52",

"ldrscanr" : "153",

"ldrpulsr" : "687 (343.5 per channel)",

"ldrpulsd" : "3",

"ldrpulsw" : "0.90",

"ldrwavel" : "1064",

"ldrmpia" : "1",

"ldrbmdiv" : "0.25",

"ldrswatw" : "2338",

"ldrswato" : "15",

"ldrgeoid" : "National Geodetic Survey (NGS) Geoid12B"

},

"ldrinfo" : {

"ldrspec" : "U.S. Geological Survey (USGS) - National Geospatial Program (NGP) Lidar Base Specification v1.2",

"ldrsens" : "Riegl VQ-Q1560i",

"ldrmaxnr" : "15",

"ldrnps" : "0.70",

"ldrdens" : "2",

"ldranps" : "0.70",

"ldradens" : "2",

"ldrfltht" : "2087",

"ldrfltsp" : "150",

"ldrscana" : "58.52",

"ldrscanr" : "153",

"ldrpulsr" : "687 (343.5 per channel)",

"ldrpulsd" : "3",

"ldrpulsw" : "0.90",

"ldrwavel" : "1064",

"ldrmpia" : "1",

"ldrbmdiv" : "0.25",

"ldrswatw" : "2338",

"ldrswato" : "15",

"ldrgeoid" : "National Geodetic Survey (NGS) Geoid12B"

},

"ldrinfo" : {

"ldrspec" : "U.S. Geological Survey (USGS) - National Geospatial Program (NGP) Lidar Base Specification v1.2",

"ldrsens" : "Riegl VQ-780i",

"ldrmaxnr" : "15",

"ldrnps" : "1.0",

"ldrdens" : "1.0",

"ldranps" : "0.70",

"ldradens" : "2.0",

"ldrfltht" : "1600",

"ldrfltsp" : "100",

"ldrscana" : "60",

"ldrscanr" : "74",

"ldrpulsr" : "300",

"ldrpulsd" : "3",

"ldrpulsw" : "0.8994",

"ldrwavel" : "1064",

"ldrmpia" : "1",

"ldrbmdiv" : "0.25",

"ldrswatw" : "1848",

"ldrswato" : "55",

"ldrgeoid" : "National Geodetic Survey (NGS) Geoid12B"

},

"ldrinfo" : {

"ldrspec" : "U.S. Geological Survey (USGS) - National Geospatial Program (NGP) Lidar Base Specification v1.2",

"ldrsens" : "Riegl VQ-1560i",

"ldrmaxnr" : "15",

"ldrnps" : "0.70",

"ldrdens" : "2",

"ldranps" : "0.70",

"ldradens" : "2",

"ldrfltht" : "1600",

"ldrfltsp" : "100",

"ldrscana" : "57",

"ldrscanr" : "82",

"ldrpulsr" : "350x2",

"ldrpulsd" : "3",

"ldrpulsw" : "0.8994",

"ldrwavel" : "1064",

"ldrmpia" : "1",

"ldrbmdiv" : "0.25",

"ldrswatw" : "1737",

"ldrswato" : "30",

"ldrgeoid" : "National Geodetic Survey (NGS) Geoid12B"

},

"ldraccur" : {

"ldrchacc" : "0.689",

"rawnva" : "0.129",

"rawnvan" : "125",

"clsnva" : "0.139",

"clsnvan" : "128",

"clsvva" : "0.186",

"clsvvan" : "96"

},

"lasinfo" : {

"lasver" : "1.4",

"lasprf" : "6",

"laswheld" : "Withheld (ignore) points were identified in these files using the standard LAS Withheld bit.",

"lasolap" : "Swath "overage" points were identified in these files using the standard LAS overlap bit.",

"lasintr" : "16",

"lasclass" : {

"clascode" : "1",

"clasitem" : "Processed, but Unclassified"

},

"lasclass" : {

"clascode" : "2",

"clasitem" : "Bare Earth Ground"

},

"lasclass" : {

"clascode" : "7",

"clasitem" : "Low Noise"

},

"lasclass" : {

"clascode" : "9",

"clasitem" : "Water"

},

"lasclass" : {

"clascode" : "10",

"clasitem" : "Ignored Ground"

},

"lasclass" : {

"clascode" : "17",

"clasitem" : "Bridge Decks"

},

"lasclass" : {

"clascode" : "18",

"clasitem" : "High Noise"

}

}}

Any conclusions drawn from the analysis of this information are not the responsibility of NOAA, the Office for Coastal Management or its partners

Data is available online for bulk or custom downloads

None

Users should be aware that temporal changes may have occurred since this data set was collected and 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.

Riegl RiProcess; GeoCue; Microstation; Terrascan; ArcGIS 10.x; Windows 8; .las X GB

This data set was produced to meet ASPRS Positional Accuracy Standard for Digital Geospatial Data (2014) for a 10-cm RMSEz Vertical Accuracy Class.

For the Virginia West Chesapeake Bay Watershed Lidar Project, the tested RMSEz of the classified lidar data for checkpoints in non-vegetated terrain equaled 7.1 cm compared with the 10 cm specification; and the non-vegetated vertical accuracy (NVA) of the classified lidar data computed using RMSEz x 1.9600 was equal to 13.9 cm, compared with the 19.6 cm specification.

The tested vegetated vertical accuracy (VVA) of the classified lidar data computed using the 95th percentile was 18.6 cm, compared with the 29.4 cm specification.

These LAS data files include all data points collected. No points have been removed or excluded, including synthetic points. Additional information regarding the synthetic points can be found in the final project report delivered to USGS. A visual qualitative assessment was performed to ensure data completeness. No void areas or missing data exist. The raw point cloud is of good quality and data passes Non-Vegetated Vertical Accuracy specifications.

Data covers the entire area specified for this project.

Data is backed up to cloud storage.