2012 USACE HSDRRS Lidar DEM: 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 (DEMs) 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.

In addition to this 2 ft bare earth DEM data, the lidar point data, that these DEMs were created from are also available. These data are available for download here: https://coast.noaa.gov/dataviewer/#/lidar/search/where:ID=6350

Breaklines created from the lidar are also available for download in shp format at: https://noaa-nos-coastal-lidar-pds.s3.amazonaws.com/laz/geoid12b/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.

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/geoid12b/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/geoid12b/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=6352;

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 ;

The TIN models are hydro enforced with breaklines of significant

hydro features (> 100ft width) such as bayous, stream banks, or lakes. Existing breakline data

sets shall be used to the furthest extent possible to minimize manual collection of additional

break lines. The breaklines compiled for the FEMA 2001/2003 LIDAR as well as the 1998 land

and water interface polylines shall be used along the HSDRRS levees as necessary to support

creation of final DEMs.

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.

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The creation of Triangular Irregular Network (TIN) elevation models and apply linear interpolation procedures to generate

the gridded DEMs at uniform post spacing. TIN post spacing should be smaller than the gridded DEM post spacing. The TIN models should be hydro enforced with breaklines of significant hydro features (> 100ft width) such as bayous, stream banks, or lakeAll data is complete to standards as specified.

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

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.