2016 USGS Lidar: Assateague Island, Maryland and Virginia, Post-Hurricane Hermine, 10-12 September 2016

Binary point-cloud data were produced for Assateague Island, Maryland and Virginia, post-Hurricane Hermine, from remotely sensed, geographically referenced elevation measurements collected by Quantum Spatial using a Riegl VQ-880-G (532-nm wavelength circular scan and 1064-nm wavelength linear scan) lidar sensor.

The purpose of this project was to produce a highly detailed and accurate digital elevation map for Assateague Island, Maryland and Virginia for use as a management tool and to make these data available to natural-resource managers and research scientists. To ensure that SPCMSC data management protocols were followed, this survey was assigned a USGS field activity number (FAN), 16CNT03. Additional survey and data details are available at http://cmgds.marine.usgs.gov/fan_info.php?fan=16CNT03. USGS Contract: G16PC00016 Task Order Number: G16D01063

Processed data products are used by the U.S. Geological Survey (USGS) CMGP's National Assessment of Coastal Change Hazards project to quantify the vulnerability of shorelines to coastal change hazards such as severe storms, sea-level rise, and shoreline erosion and retreat.

The following are the USGS lidar fields in JSON:

{

"ldrinfo" : {

"ldrspec" : "U.S. Geological Survey National Geospatial Program lidar Base Specification, Version 1.2",

"ldrsens" : "Riegl VQ-880-G",

"ldrmaxnr" : "Unlimited",

"ldrnps" : "0.7",

"ldrdens" : "2",

"ldranps" : "0.7",

"ldradens" : "2",

"ldrfltht" : "500",

"ldrfltsp" : "120",

"ldrscana" : "40",

"ldrscanr" : "160",

"ldrpulsr" : "245",

"ldrpulsd" : "1.3",

"ldrpulsw" : "35",

"ldrwavel" : "532",

"ldrmpia" : "0",

"ldrbmdiv" : "0.7",

"ldrswatw" : "364",

"ldrswato" : "50",

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

},

"ldraccur" : {

"ldrchacc" : "19.6",

"rawnva" : "0.072",

"rawnvan" : "13"

},

"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" : "17",

"clasitem" : "Bridge Decks"

},

"lasclass" : {

"clascode" : "40",

"clasitem" : "Bathymetric Bottom"

},

"lasclass" : {

"clascode" : "41",

"clasitem" : "Water Surface"

},

"lasclass" : {

"clascode" : "45",

"clasitem" : "Water Column"

}

}}

Although these data have been processed successfully on a computer system at the USGS, no warranty expressed or implied is made regarding the display or utility of the data on any other system, or for general or scientific purposes, nor shall the act of distribution constitute any such warranty. The USGS shall not be held liable for improper or incorrect use of the data described and/or contained herein. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.

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 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.

Microsoft Windows 7 Enterprise Service Pack 1; Esri ArcCatalog 10.2.2.3552

Quantum Spatial reports that the contract specifications required that raw Non-vegetated Vertical Accuracy (NVA) be computed from the both the raw lidar point cloud swath files and the derived DEMs. Additionally, Vegetated Vertical Accuracy (VVA) was also to be computed from the derived DEMS. The NVA was tested with 13 independent check points provided to QSI by USGS located in open terrain, and distributed throughout the project as feasible. These check points were not used in the calibration or post processing of the lidar point cloud data. The VVA was tested with 12 independent check points, also provided to QSI by USGS, located in vegetated terrain and also witheld from the calibration and post processing of the lidar point cloud data. VVA points were also distributed throughout the project area as feasible. Specifications for this project require that the NVA be 19.6 meters or better AccuracyZ at 95% confidence level and that the VVA be 29.4 cm or better AccuracyZ at the 95th percentile. NVA Root Mean Square Error (RMSE) was calculated using the 13 independent check points provided by the USGS and resulted in a value of 0.072m.Qualitative value:0.072 meters AccuracyZ at the 95 percent Confidence Interval for Raw LAS NVA. 0.063 meters AccuracyZ at the 95 percent Confidence Interval for DEM NVA. 0.137 meters AccuracyZ at the 95th percentile for DEM VVA., Test that produced the value: Quantum Spatial reports that the 13 independent NVA check points were surveyed using the closed level loop technique. Elevations interpolated from the unclassified lidar surface were compared to the elevation values of the surveyed NVA check points. The RMSE was computed to be 0.037 meters resulting in an AccuracyZ at the 95% confidence level of 0.072 meters. The 13 NVA check points were also compared to the elevations of the derived bare earth DEMs. The RMSE was computed to be 0.032 meters resulting in an AccuracyZ of 0.063 meters at the 95% confidence level. NVA AccuracyZ has been tested and meets the required 19.6 meter NVA at 95% confidence level using (RMSEz * 1.9600) for both the raw lidar point cloud and derived DEMs, as defined by the National Standards for Spatial Data Accuracy (NSSDA) and herein reported using National Digital Elevation Program (NDEP)/ASPRS Guidelines. The 13 VVA check points were also surveyed using the closed level loop technique. Elevations for these points were compared to the elevations of the derived bare earth DEMs. The RMSE was computed to be 0.078 meters resulting in an AccuracyZ of 0.137 meters at the 95th percentile. AccuracyZ has been tested on the derived bare earth DEMs and meets the required 29.4 meter VVA using the 95th percentile of the absolute value of all vertical errors in all combined vegetation classes as defined by the National Standards for Spatial Data Accuracy (NSSDA); and herein reported using National Digital Elevation Program (NDEP)/ASPRS Guidelines.

Quantum Spatial reports that these LAS files include all data points collected. No points have been removed or excluded. Shaded relief images have been visually inspected for data errors such as pits, border artifacts, and shifting. Lidar flight lines have been examined to ensure consistent elevation values across overlapping flight lines. The raw point cloud is of good quality and data passes Vertical Accuracy specifications.

Quantum Spatial reports that data cover the entire area specified for this project, approximately 52,196.2 acres.