2019 USACE NCMP DUNEX Topobathy Lidar DEM: East Coast (NC, VA)

These files contain rasterized topobathy lidar elevations generated from data collected by the Coastal Zone Mapping and Imaging Lidar (CZMIL) system.CZMIL integrates a lidar sensor with simultaneous topographic and bathymetric capabilities, a digital camera and a hyperspectral imager on a single remote sensing platform for use in coastal mapping and charting activities. Native lidar data is not generally in a format accessible to most Geographic Information Systems (GIS). Specialized in-house and commercial software packages are used to process the native lidar data into 3-dimensional positions that can be imported into GIS software for visualization and further analysis. Horizontal positions, provided in decimal degrees of latitude and longitude, are referenced to the North American Datum of 1983 National Adjustment of 2011 (NAD83 (2011)). Vertical positions are referenced to the NAD83 (2011) ellipsoid and provided in meters. The National Geodetic Survey's (NGS) GEOID12B model is used to transform the vertical positions from ellipsoid to orthometric heights referenced to the North American Vertical Datum of 1988 (NAVD88). The 3-D position data are sub-divided into a series of LAS files, which are tiled into 1-km by 1-km boxes defined by the Military Grid Reference System.

This data was provided to the NOAA Office for Coastal Management (OCM) for data distribution from the Data Access Viewer (DAV). The raster bare earth DEM data are available for custom and bulk download. In addition to these bare earth Digital Elevation Model (DEM) data, the lidar point data that these DEM data were created from and the associated imagery collection are also available. These data are available for custom download at the links provided in the URL section of this metadata record.

Original contact information:

Contact Org: JALBTCX

Title: Data Production Manager

Phone: 228-252-1131

Email: JALBTCX@usace.army.mil

This data was collected by the USACE in support of the U.S. Coastal Research Program DUNEX collaborative experiment to assess changes in elevation above and below water along the coast of North Carolina. This dataset provides a repeat lidar elevation coverage from late Fall 2019 to be compared with an earlier coverage acquired in early Summer 2019 to assess coastal change over a single hurricane season and provide a regional context for a variety of DUNEX research projects. More information about DUNEX: https://uscoastalresearch.org/dunex

These data have been developed from the best available sources. Although efforts have been made to ensure that the data are accurate and reliable, errors and variable conditions originating from physical sources used to develop the data may be reflected in the data supplied. Users must be aware of these conditions and bear responsibility for the appropriate use of the information with respect to possible errors, scale, resolution, rectification, positional accuracy, development methodology, time period, environmental and climatic conditions and other circumstances specific to these data. The user is responsible for understanding the accuracy limitations of the data provided herein. The burden for determining fitness for use lies entirely with the user. The user should refer to the accompanying metadata notes for a description of the data and data development procedures. Any conclusions drawn from the analysis of this information are not the responsibility of USACE, JALBTCX, NOAA, the Office for Coastal Management, or its partners.

Data is available online for bulk and custom downloads.

These data have been developed from the best available sources. Although efforts have been made to ensure that the data are accurate and reliable, errors and variable conditions originating from physical sources used to develop the data may be reflected in the data supplied. Users must be aware of these conditions and bear responsibility for the appropriate use of the information with respect to possible errors, scale, resolution, rectification, positional accuracy, development methodology, time period, environmental and climatic conditions and other circumstances specific to these data. The user is responsible for understanding the accuracy limitations of the data provided herein. The burden for determining fitness for use lies entirely with the user. The user should refer to the accompanying metadata notes for a description of the data and data development procedures.

These data depict the heights at the time of the survey and are only accurate for that time. Acknowledgement of the Joint Airborne Lidar Bathymetry Technical Center of eXpertise (JALBTCX) would be appreciated in any publications or derived products. The data herein, including but not limited to geographic data, tabular data, analytical data, electronic data structures or files, are provided "as is" without warranty of any kind, either expressed or implied, or statutory, including, but not limited to, the implied warranties or merchantability and fitness for a particular purpose. The entire risk as to the quality and performance of the data is assumed by the user. No guarantee of accuracy is granted, nor is any responsibility for reliance thereon assumed. In no event shall the U.S. Army Corps of Engineers, Mobile District Office, Spatial Data Branch be liable for direct, indirect, incidental, consequential or special damages of any kind, including, but not limited to, loss of anticipated profits or benefits arising out of use of or reliance on the data. The Spatial Data Branch does not accept liability for any damages or misrepresentation caused by inaccuracies in the data or as a result of changes to the data caused by system transfers or other transformations or conversions, nor is there responsibility assumed to maintain the data in any manner or form. Users should be aware that temporal changes may have occurred since this dataset was collected and that some parts of these data may no longer represent actual surface conditions. Users should not use these data for critical applications without a full awareness of its limitations.

Microsoft Windows 7 Version 6.1 (Build 7601) Service Pack 1; Esri ArcGIS 10.5.0.6491

CZMIL topographic data - Compiled to meet 1 m horizontal accuracy at 95% confidence level. CZMIL bathymetric data - Compiled to meet 3.5 + 0.05d m horizontal accuracy at 95% confidence level, d is depth.

JALBTCX evaluates the horizonal accuracy of the final data coverage against availlable basemap imagery products. The final lidar point cloud is gridded according to proceedures defined in the JALBTCX Standard Operating Guide and Appendices (SOGA). The grid products are then visually compared to basemap imagery products to verify the horizontal positions of large buildings and other urban features with the data coverage

CZMIL topographic data - Compiled to meet 20 cm vertical accuracy at 95% confidence level. CZMIL bathymetric shallow FOV data - Compiled to meet SQRT((0.20^2) +((0.0075d)^2)) m vertical accuracy at 95% confidence level, d is depth. CZMIL bathymetric deep FOV data - Compiled to meet SQRT((0.30^2) +((0.013d)^2)) m vertical accuracy at 95% confidence level, d is depth.

JALBTCX evaluates the vertical accuracy of the final data coverage against traditional ground-truth data. Ground-truth data is acquired and utilized according to specifications outlined in the JALBTCX Standard Operating Guide and Appendices (SOGA) as well as the USGS Lidar BaseSpecification. The final lidar point cloud at every project ground-truth location is compared against ground-truth points in the 'bare_ground' class. Comparisons are performed in the QCoherent LP360 software package, and the final results are output to JALBTCX's Ground Truth Comparison Report.

Every effort within operational constraints was made to achieve the intended data coverage and planned point densities.

Planned data coverage for this dataset includes the shoreline from the NC/VA Border to Cape Lookout, NC. Lidar and imagery data acquisition was focused on a 1500 meter swath of the shoreline that generally extends from the shoreline onshore 500 meters and from the shoreline offshore to 1000 meters or laser extinction, whichever occurs first. The planned point spacing is 90 centimeters on land and in shallow water. In deeper water the planned point spacing is 2 meters. Gaps or data holidays exist in the bathymetric portion of the data coverage due to a number of operational and environmental conditions, including by not limited to, active surf, low-reflectivity bottom substrate materials and turbidity in the water column. Please see the Report of Survey for additional details.

Every effort within operational constraints was made to acquire data that meets specifications as outline in this project's Statement of Work. Per flight block, elevations in areas of swath overlap are internally consistent and meet CZMIL specifications. Anomalous high and/or low elevation values have been removed, and point cloud classification algorithms have been validated via manual review and QC. Temporal differences in elevation exist in areas of active near shore processes from the dune to the depth of closure. JALBTCX conducts operations in a manner to ameliorate temporal differences, to include the collection of entire flight blocks within single missions. For a given flight block, it's adjacent flight blocks are captured within 3 days as weather and airspace permit.

JALBTCX evaluates final data coverage using techniques that are common to the lidar industry. These techniques are performed in a 3D environment for visual review of the final data coverage and verification of data alongside lidar waveforms and imagery collected concurrent with the lidar. Data reviewers perform checks to verify (1) extreme high and/or low elevation values have been invalidated, (2) elevations in areas of swath overlap are internally consistent, (3) binned standard deviation values meet CZMIL specifications, (4) point cloud classifications are valid, and (4) CZMIL processing modes are valid.

Data is backed up to tape and to cloud storage.

CZMIL data is processed from raw lidar waveforms to point clouds using the CZMIL HydroFusion software package. Point clouds are then classified and edited in industry-standard software packages. Derivative data products are generated through the application of gridding and contouring algorithms in a GIS environment. The data processing workflow, including software packages, algorithms and parameters are provided in detail, herein this metadata as Process Steps.