2018 USGS Lidar: Post Hurricane Maria - Puerto Rico

This data set was retrieved from the USGS rockyftp website and processed to NOAA/OCM's Digital Coast.

Product: These lidar data are processed Classified LAS 1.4 files, formatted to 4,376 individual 1500 m x 1500 m tiles; used to create intensity images, 3D breaklines and hydro-flattened DEMs as necessary.

Geographic Extent: Puerto Rico, covering approximately 3,585 square miles.

Dataset Description: PR USVI Lidar project called for the Planning, Acquisition, processing and derivative products of lidar data to be collected at a nominal pulse spacing (NPS) of 0.35 meter. Project specifications are based on the U.S. Geological Survey National Geospatial Program Base Lidar Specification, Version 1.3. The data was developed based on a horizontal projection/datum of NAD83 (2011), Puerto Rico and Virgin Islands, meters and vertical datum of PRVD02 (GEOID12B), meters. Lidar data was delivered as processed Classified LAS 1.4 files, formatted to 4,374 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 in late 2018, while no snow was on the ground and rivers were at or below normal levels. Cloud cover prevented the acquisition of portions of the island, mainly in the east. In order to post process the lidar data to meet task order specifications and meet ASPRS vertical accuracy guidelines, Leading Edge Geomatics established a total of 112 ground control points that were used to calibrate the lidar to known ground locations established throughout the Puerto Rico project area. An additional 167 independent accuracy checkpoints, 96 in Bare Earth and Urban landcovers (96 NVA points), 71 in Tall Grass and Brushland/Low Trees categories (71 VVA points), were used to assess the vertical accuracy of the data. These checkpoints were not used to calibrate or post process the data.

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 0.5 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 SUBCONTRACTOR: Leading Edge Geomatics Lidar data were acquired and calibrated by Leading Edge Geomatics. 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 v1.3",

"ldrsens" : "Riegl VQ1560i",

"ldrmaxnr" : "Infinite",

"ldrnps" : "0.31",

"ldrdens" : "10.3",

"ldranps" : "0.31",

"ldradens" : "10.3",

"ldrfltht" : "1000",

"ldrfltsp" : "150",

"ldrscana" : "57",

"ldrscanr" : "175x2",

"ldrpulsr" : "700x2",

"ldrpulsd" : "3",

"ldrpulsw" : "0.8994",

"ldrwavel" : "1064",

"ldrmpia" : "1",

"ldrbmdiv" : "0.25",

"ldrswatw" : "1086",

"ldrswato" : "20",

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

},

"ldrinfo" : {

"ldrspec" : "U.S. Geological Survey (USGS) - National Geospatial Program (NGP) Lidar Base Specification v1.3",

"ldrsens" : "Riegl Q780",

"ldrmaxnr" : "Infinite",

"ldrnps" : "0.42",

"ldrdens" : "5.7",

"ldranps" : "0.30",

"ldradens" : "11.4",

"ldrfltht" : "800",

"ldrfltsp" : "100",

"ldrscana" : "60",

"ldrscanr" : "122",

"ldrpulsr" : "400",

"ldrpulsd" : "3",

"ldrpulsw" : "0.8994",

"ldrwavel" : "1064",

"ldrmpia" : "1",

"ldrbmdiv" : "0.25",

"ldrswatw" : "924",

"ldrswato" : "50",

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

},

"ldraccur" : {

"ldrchacc" : "0.341",

"rawnva" : "0.148",

"rawnvan" : "91",

"clsnva" : "0.132",

"clsnvan" : "96",

"clsvva" : "0.270",

"clsvvan" : "71"

},

"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" : "17",

"clasitem" : "Bridge Decks"

},

"lasclass" : {

"clascode" : "18",

"clasitem" : "High Noise"

},

"lasclass" : {

"clascode" : "20",

"clasitem" : "Ignored Ground"

}

}}

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 software for initial point cloud processing; GeoCue; Microstation/Terrascan; ArcGIS 10.5; Windows 7 Operating System

The island of Puerto Rico and its surrounding islands were produced to meet ASPRS Positional Accuracy Standards for Digital Geospatial Data (2014) for a 41 cm RMSEx/RMSEy Horizontal Accuracy Class which equates to Positional Horizontal Accuracy = +/- 1 meter at a 95% confidence level.

Seventeen (17) checkpoints were photo-identifiable but do not produce a statistically significant tested horizontal accuracy value. Using this small sample set of photo identifiable checkpoints, positional accuracy of this dataset was found to be RMSEx = 15.5 cm and RMSEy = 12.2 cm which equates to +/- 34.1 cm at 95% confidence level. While not statistically significant, the results of the small sample set of checkpoints are within the produced to meet horizontal accuracy

For the island of Puerto Rico and its surrounding islands, the tested RMSEz of the classified lidar data for checkpoints in non-vegetated terrain equaled 6.8 cm compared with the 10 cm specification; and the NVA of the classified lidar data computed using RMSEz x 1.9600 was equal to 13.2 cm, compared with the 19.6 cm specification.

For the island of Puerto Rico and its surrounding islands, the tested VVA of the classified lidar data computed using the 95th percentile was equal to 27.0 cm, compared with the 29.4 cm specification.

The project specifications require that only Non-Vegetated Vertical Accuracy (NVA) be computed for raw lidar point cloud swath files. The required accuracy (ACCz) is: 19.6 cm at a 95% confidence level, derived according to NSSDA, i.e., based on RMSE of 10 cm in the "bare earth" and "urban" land cover classes. The NVA of Puerto Rico, the U.S. Virgin Islands, and the surrounding islands will be tested with 91 checkpoints located in bare earth and urban (non-vegetated) areas. These check points were not used in the calibration or post processing of the lidar point cloud data. The checkpoints were distributed throughout the project area and were surveyed using GPS techniques. See survey report for additional survey methodologies.

Elevations from the unclassified lidar surface were measured for the x,y location of each check point. Elevations interpolated from the lidar surface were then compared to the elevation values of the surveyed control points. AccuracyZ will be tested to meet 19.6 cm or better Non-Vegetated Vertical Accuracy at 95% confidence level using RMSE(z) x 1.9600 as defined by the National Standards for Spatial Data Accuracy (NSSDA); assessed and reported using National Digital Elevation Program (NDEP)/ASRPS Guidelines.

These LAS data files include all data points collected. No points have been removed or excluded. A visual qualitative assessment was performed to ensure data completeness. 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. Because parts of the PR USVI 2018 Lidar project were collected in areas where there are clouds virtually every day of the year, there are some ground voids. With the current available technology, lidar sensors cannot penetrate clouds. The noise from clouds was removed from the classified lidar dataset, however, this resulted in some areas having ground voids.

Data is backed up to tape and to cloud storage.