2012 USACE HSDRRS Lidar: New Orleans

Acquisition of Light Detection and Ranging (LiDAR) elevation data was for the Hurricane and Storm Damage Risk Reduction System (HSDRRS). In February 2012,

USACE, Contracting Division contracted with The Atlantic Group to provide acquisition of Light Detection and Ranging (LiDAR) elevation data in the Hurricane and Storm Damage Risk Reduction System, St. Charles, Jefferson, Orleans, St. Bernard and Plaquemines Parishes, LA. This data will be used to support interior drainage modeling. LiDAR data should be collected to fully capture the total interior of the HSDRRS, including floodwalls, structures, and levees, and 200 feet outside of the HSDRRS to water's edge as appropriate. The project shall include capture of LiDAR data and the creation of digital elevation models derived from the LiDAR. The project area is approximately 418.4 sq. miles, including a 200' buffer. The purpose of the survey is to obtain measurements of the bare ground surface, as well as top surface feature elevation data for providing geometry input to USACE hydrodynamic and other numerical models as well as for performing economic related assessments.

Upon receipt of data, the NOAA Office for Coastal Management (OCM) noted that many areas have lidar points over water that are classified as ground. This was mainly seen in lidar points over Lake Pontchartrain. In these areas, those points were reclassified from ground (2) to unclassified (1). In other areas, however, the user should be aware that points over water may be classified as ground.

In addition to the lidar point data, bare earth Digital Elevation Models (DEMs), at a 2 ft grid spacing, created from the lidar point data are also available. These data are available for download here: https://coast.noaa.gov/dataviewer/#/lidar/search/where:ID=6352

Breaklines created from the lidar are also available for download in shp format at: https://noaa-nos-coastal-lidar-pds.s3.amazonaws.com/laz/geoid18/6350/breaklines

The DEM and breakline products have not been reviewed by the NOAA Office for Coastal Management (OCM) and any conclusions drawn from the analysis of this information are not the responsibility of NOAA, OCM or its partners.

Original contact information:

Contact Name: Patrick Robinson

Contact Org: Atlantic Group

Title: LiDARManager

Phone: 256-971-9991

Email: probinson@theatlgrp.com

The purpose of the survey is to obtain measurements of the bare ground surface, as well as top surface feature elevation data for providing geometry input to USACE hydrodynamic and other numerical models as well as for performing economic related assessments.

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The lidar report may be accessed here:

https://noaa-nos-coastal-lidar-pds.s3.amazonaws.com/laz/geoid18/6350/supplemental/la2012_usace_new_orleans_m6350_lidar_report.pdf

The survey report may be accessed here:

https://noaa-nos-coastal-lidar-pds.s3.amazonaws.com/laz/geoid18/6350/supplemental/la2012_usace_new_orleans_m6350_survey_report.pdf

Any conclusions drawn from the analysis of this information are not the responsibility of the Atlantic Group, USACE, NOAA, the NOAA Office for Coastal Management (OCM) or its partners.

N/A

Nothing Specified

This data can be obtained on-line at the following URL: https://coast.noaa.gov/dataviewer/#/lidar/search/where:ID=6350;

None

None. However, 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. Acknowledgement of the U.S. Geological Survey would be appreciated for products derived from these data.

ArcMAP V.10.1 ; LP360 V.2011.1.54.1 ; Microstation V8 ; ALTMnav ; Dashmap ;

A minimum of 20 test points where selected for each land cover class (except HSDRRS Class 7) identified per 100 Sq miles. Therefore, 120 test points were selected for the six land cover classes specified above per 100 Sq miles, plus 20 test points each for any additional land cover classes added. Additionally, test points were geographically distributed throughout the project area. Test points were carefully selected in areas of the highest PDOP to evaluate DEM accuracy under trees and in vegetation representative of the study area. A minimum of 50 test points was collected along the HSDRRS levees to enable an accuracy assessment for the HSDRRS. These levee test points where spaced at least 0.25 miles apart, but they do not need to cover the entire HSDRRS levee system.

The data must meet the NSSDA RMSEr of 2.2 ft (0.67 m) and the NSSDA Accuracyr of 95% confidence level is 3.80 ft (1.16 m). Horizontal point accuracy is a function of angular origination of the pulse; IMU orientation; the scanner encoder and ranging function and will vary depending on the proposed point density selected for the collection. Statistically, the error is roughly 1/3 of the illuminated foot print on the ground and is a function of the beam divergences.

Based on the vertical accuracy testing conducted by The Atlantic Group, LLC using NSSDA methodology, the dataset tested 12.2 cm for vertical accuracy at 95% confidence level in open terrain. LiDAR vertical data accuracy determination shall employ the National Standard for Spatial Data Accuracy (NSSDA). Contracted to meet 18cm (RMSE) or better.

All data is complete to standards as specified.LIDAR raster data is visually inspected for completeness to ensure that any gaps between flight lines of required collection area. LIDAR is self-illuminating and has minimal cloud penetration capability. Water vapor in steam plumes or particulates in smoke may cause reflection of LIDAR signals and loss of elevation information beneath these plumes. Glass structures and roofs may appear transparent to the LIDAR signal and therefore may not register on the reflective surface.

QC/QA process shall include reviews of flight alignments and

completeness of supporting data. The USACE New Orleans district or its designee may perform

additional QC/QA testing. The root mean square error (RMSE) is used to estimate both

horizontal and vertical accuracy. RMSE is the square root of the average of the set of squared

differences between dataset coordinate values and coordinate values from an independent source.

Bare-earth processed data for this acquisition block comply with the following accuracy requirements for Artifact/Feature removal: artifacts - 90%; outliers - 95%; vegetation - 95%; buildings - 98%. All LAS formatted LIDAR data are validated using commercial GIS software to ensure proper formatting and loading before delivery. This validation procedure ensures that data on delivery media is in correct physical format and is readable.

of higher accuracy for identical points. If those differences are normally distributed and average

zero, 95 percent of any sufficiently large sample should be less than 1.96 times the RMSE.

Therefore 9-centimeter RMSE can be referred to as "18-centimeter accuracy at the 95-percent

confidence level." Following that convention, the vertical accuracy of any DEM is defined as

1.96 times the RMSE of linearly interpolated elevations in the DEM, as compared with known

elevations from high-accuracy test points. DEMs should have a maximum RMSE as specified to

meet its required vertical accuracy. The contractor must field verify the vertical accuracy of this

DEM to ensure that the RMSE requirement is satisfied for all land cover classes that

predominate within the floodplain being studied.