2021 USGS Lidar: Coastal Louisiana

Product:

These lidar data are processed Classified LAS 1.4 files, formatted to individual 1,000 m x 1,000 m tiles; used to create intensity images, 3D breaklines and hydro-flattened DEMs as necessary.

Geographic Extent:

LA_CoastalLouisiana_1 (Work Unit 197958) covering approximately 2,200 square miles in Jefferson, Orleans, Plaquemines, and St. Bernard Parishes

LA_CoastalLouisiana_2 (Work Unit 228382) covering approximately 734 square miles in Jefferson, Lafourche, Plaquemines, and St. Charles Parishes

Dataset Description:

The LA Coastal Louisiana 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 meters. Project specifications are based on the U.S. Geological Survey National Geospatial Program Base Lidar Specification, Version 2.1. The data were developed based on a horizontal datum/projection of NAD83 (2011) UTM Zone 15N (LA_CoastalLouisiana_2 (Work Unit 228382)) and 16N (LA_CoastalLouisiana_1 (Work Unit 197958)), Universal Transverse Mercator, meters and a vertical datum of NAVD88 (GEOID18), meters. Lidar data was delivered as processed Classified LAS 1.4 files, formatted to individual 1,000 m x 1,000 m tiles, as tiled Intensity Imagery, and as tiled bare earth DEMs; all tiled to the same 1,000 m x 1,000 m schema.

Ground Conditions:

Lidar was collected in early 2021 and late 2021, while no snow was on the ground and rivers were at or below normal levels.

LA_CoastalLouisiana_1

In order to post process the lidar data to meet task order specifications and meet ASPRS vertical accuracy guidelines, Dewberry, established a total of 34 ground control points that were used to calibrate the LA_CoastalLouisiana_1 (Work Unit 197958) lidar to known ground locations established throughout the LA Coastal Louisiana project area. An additional 111 independent accuracy checkpoints, 62 in Bare Earth and Urban landcovers (62 NVA points), 49 in Tall Grass and Brushland/Low Trees categories (49 VVA points), were used to assess the vertical accuracy of the data. These checkpoints were not used to calibrate or post process the data.

LA_CoastalLouisiana_2

In order to post process the lidar data to meet task order specifications and meet ASPRS vertical accuracy guidelines, Dewberry, established a total of 17 ground control points that were used to calibrate the LA_CoastalLouisiana_2 (Work Unit 228328) lidar to known ground locations established throughout the LA Coastal Louisiana 2020 project area. An additional 48 independent accuracy checkpoints, 31 in Bare Earth and Urban landcovers (31 NVA points), 17 in Tall Grass and Brushland/Low Trees categories (17 VVA points), were used to assess the vertical accuracy of the data. These checkpoints were not used to calibrate or post process the data.

The NOAA Office for Coastal Management (OCM) downloaded laz point data files from this USGS rockyweb site (https://rockyweb.usgs.gov/vdelivery/Datasets/Staged/Elevation/LPC/Projects/LA_CoastalLouisiana_2020_D20/). The data were processed to the NOAA Digital Coast Data Access Viewer (DAV) to make the data available for custom downloads.

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: Digitial Aerial Solutions, LLC Lidar data were acquired and calibrated by Digitial Aerial Solutions. 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 v2.1",

"ldrsens" : "ALS80_HP SN#8235",

"ldrmaxnr" : "5",

"ldrnps" : "0.29",

"ldrdens" : "8",

"ldranps" : "0.29",

"ldradens" : "8",

"ldrfltht" : "1277",

"ldrfltsp" : "155",

"ldrscana" : "30",

"ldrscanr" : "58.4",

"ldrpulsr" : "642.8",

"ldrpulsd" : "3",

"ldrpulsw" : "0.31",

"ldrwavel" : "1064",

"ldrmpia" : "1",

"ldrbmdiv" : "0.15",

"ldrswatw" : "684.61",

"ldrswato" : "30",

"ldrgeoid" : "National Geodetic Survey (NGS) Geoid18"

},

"ldraccur" : {

"ldrchacc" : "0",

"rawnva" : "0",

"rawnvan" : "0"

},

"lasinfo" : {

"lasver" : "1.4",

"lasprf" : "6",

"laswheld" : "Withheld (ignore) points were identified in these files using the standard LAS Withheld bit. Noise classes, Class 7 and Class 18, were assigned the LAS withheld bit.",

"lasolap" : "Swath "overage" points are assigned per the producer's discretion. Dewberry did not classify overage points.",

"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"

},

"lasclass" : {

"clascode" : "32",

"clasitem" : "Levee"

}

}}

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 and 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.

Leica CloudPro; LP360; Microstation; Terrascan; ArcGIS 10.6; Windows 8; .las 1510 GB

Only checkpoints photo-identifiable in the intensity imagery can be used to test the horizontal accuracy of the lidar. Photo-identifiable checkpoints in intensity imagery typically include checkpoints located at the ends of paint stripes on concrete or asphalt surfaces or checkpoints located at 90 degree corners of different reflectivity, e.g. a sidewalk corner adjoining a grass surface. The xy coordinates of checkpoints, as defined in the intensity imagery, are compared to surveyed xy coordinates for each photo-identifiable checkpoint. These differences are used to compute the tested horizontal accuracy of the lidar. As not all projects contain photo-identifiable checkpoints, the horizontal accuracy of the lidar cannot always be tested.

Fifteen checkpoints were determined to be photo-identifiable in the intensity imagery and were used to test the horizontal accuracy of the lidar dataset. Due to the small number of available checkpoints, the results reported herein are not considered statistically significant. Using NSSDA methodology (endorsed by the ASPRS Positional Accuracy Standards for Digital Geospatial Data (2014)), horizontal accuracy at the 95% confidence level (called Accuracyr) is computed by the formula RMSEr * 1.7308 or RMSExy * 2.448. No horizontal accuracy requirements or thresholds were provided for this project. However, this data set was produced to meet ASPRS Positional Accuracy Standards for Digital Geospatial Data (2014) for a 41 cm RMSEx/RMSEy horizontal accuracy class which equates to a positional horizontal accuracy = ± 1 meter at the 95% confidence level. Using this small sample of 15 photo-identifiable checkpoints, positional accuracy of this dataset was found to be RMSEx = 27.8 cm and RMSEy = 25.6 cm, which equates to ± 65.4 cm at the 95% confidence level (0.378 m RMSEr).

For more information see the Dewberry project report. The link to this report is provided in the URL section of this metadata record.

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

USGS Determined Vertical Accuracy:

NVA = 7.12 cm RMSEz, NVA Accuracyz at 95th confidence level = 13.95 cm

VVA = 27.65 cm at the 95th percentile

For more information see the USGS project report and the Dewberry project report. The links to these reports are provided in the URL section of this metadata record.

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. 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.

This data was collected by Dewberry for the U.S. Geological Survey USGS). The data were made available for download by USGS. The NOAA Office for Coastal Management (OCM) downloaded the data to make the data available for custom download from the NOAA OCM Digital Coast Data Access Viewer (DAV).