2018 USACE FEMA Topobathy Lidar DEM: Main Island, Culebra, and Vieques, Puerto Rico

These bare earth Digital Elevation Model (DEM) files along the Puerto Rico coast, contain rasterized topobathy lidar elevations at a 1 meter grid size, 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.

In addition to the bare earth DEMs, the topobathy lidar point data from which these DEM data were created, are also available. A link to this data is provided in the URL section of this metadata record. DEMs that were created from all classes of points (1, 2, 29) at a 1 meter grid size are available by request via email at: coastal.info@noaa.gov.

Original contact information:

Contact Org: JALBTCX

Title: Data Production Manager

Phone: 228-252-1131

Email: JALBTCX@usace.army.mil

This data was collected by USACE on behalf of FEMA as part of the Puerto Rico Shoreline Erosion Assessment Survey following Hurricane Maria to assess changes in elevations above and below water along the coast.

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 and bulk downloads.

None

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. 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.

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.

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.

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.

CZMIL topographic data - Compiled to meet 19.6 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.

Planned data coverage for this dataset included a 750-meter swath of the Puerto Rico shoreline for the main island, Culebra, and Vieques. Topographic lidar coverage was obtained from the shoreline onshore 500 meters. Bathymetric lidar coverage extends from the shoreline offshore 250 meters or to laser exinction, whichever occurs first. The planned data density is 70 centimeters on land and in shallow water. In deeper water the planned data density decreases to 2 meters. Gaps or data holidays may exist in the data coverage. They arise due to a number of operational and environmental conditions, including but not limited to, airspace restrictions, high terrain, 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 outlined in this project's Statement of Work. Per flight block, elevations in areas of swath overlap are internally consistent and meet CZMIL specifications. Annomalous high and/or low elevation values have been removed, and point cloud classificaiton algorithms have been validated via manual review and QC. Temporal differences in elevation exist in areas of active nearshore 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.

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.