2009 USACE NCMP Topobathy Lidar: AL, LA, MS, TX (Post Hurricanes Gustav & Ike)

The Light Detection and Ranging (LiDAR) LAS dataset is a topographic survey conducted for the Post Hurricane Gustav and Post Hurricane Ike Aerial Survey 2009 projects. Hurricane Gustav made US landfall at Cocodrie, LA on September 1, 2008. Hurricane Ike made US landfall near Galveston, TX on September 13, 2008. This data was produced for the US Army Corps of Engineers (USACE) Joint Airborne Lidar Bathymetry Technical Center of Expertise (JALBTCX). The LiDAR point cloud was flown at a density sufficient to support a maximum final post spacing of 1.5 points per meter. The data are classified according to ASPRS LAS specifications as: 1 (Unclassified), 2 (Ground), 3 (Low Vegetation) 4 (Medium Vegetation), 5 (High Vegetation), 6 (Building), 7 (Low Point (Noise)), and 9 (Water). 3001 International Inc. acquired the 290 flightlines between February 3, 2009 and April 23, 2009. The Post Hurricane Gustav and Post Hurricane Ike Aerial

Surveys 2009 were collected under the guidance of a Professional Mapper/Surveyor.

Original contact information:

Contact Org: 3001 International Inc.

Title: LiDAR Department

Phone: (985) 661 - 3001

Email: lidar@3001inc.com

In addition to the lidar point data, topobathy bare earth Digital Elevation Models (DEMs) at a 1 meter grid spacing, created from the lidar point data are also available from the NOAA Digital Coast. The link to this data is provided in the URL section of this metadata record.

The Post Hurricane Gustav and Post Hurricane Ike Aerial Survey 2009 projects will support the US Army Corps of Engineers (USACE) Joint Airborne Lidar Bathymetry Technical Center of Expertise (JALBTCX) collection of data representing the post-hurricane condition of the beaches, barrier islands, and lakeshores along the coasts of Alabama, Louisiana, Mississippi, and Texas following Hurricanes Gustav and Ike.

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A footprint of this data set may be viewed in Google Earth at:

https://noaa-nos-coastal-lidar-pds.s3.amazonaws.com/laz/geoid18/1061/supplemental/2009_USACE_Post_Hurricanes_Gustav_and_Ike_Topo_Lidar.kmz

Any conclusions drawn from the analysis of this information are not the responsibility of USACE, JALBTCX, the Office for Coastal Management or its partners.

Unclassified

Unclassified

This data can be obtained on-line at the following URL: https://coast.noaa.gov/dataviewer;

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.

Microsoft Windows XP Version 5.1 (Build 2600) Service Pack 3; ESRI ArcCatalog 9.2.6.1500

The Post Hurricane Gustav and Post Hurricane Ike Aerial Survey 2009 projects were collected under the guidance of a Professional Mapper/Surveyor.

The data were collected at a density sufficient to support a maximum final post spacing of 1.5 points per meter.

All ground control processing and adjustment is performed using published coordinate horizontal and vertical datums (e.g. NGS CORS). For

deliverables, Corpscon for Windows Version 5.11.08 (geoid 03) was used for horizontal and vertical datum conversion as well as for coordinate

system conversion purposes (e.g. UTM to State Plane).

; Quantitative Value: 1 meters, Test that produced the value: See entity and attribute information

The accuracy assessment was performed using a standard method to compute the root mean square error (RMSE) based on a comparison of ground

control points (GCP) and filtered LiDAR data points. Filtered LiDAR data has had vegetation and cultural features removed and by analysis

represents bare-earth elevations. The RMSE figure was used to compute the vertical National Standard for Spatial Data Accuracy (NSSDA).

Ground control was established by 3001, Inc. A spatial proximity analysis was used to select edited LiDAR data points contiguous to the

relevant GCPs. A search radius decision rule is applied with consideration of terrain complexity, cumulative error and adequate sample size.

Cumulative error results from the errors inherent in the various sources of horizontal measurement. These sources include the airborne GPS,

GCPs and the uncertainty of the accuracy of the LiDAR data points. This accuracy is achieved prior to the sub-sampling that occurs through

integration with the inertial measurement unit (IMU) positions that are recorded. It is unclear at this time whether the initial accuracy is

maintained. The horizontal accuracy of the GCPs is estimated to be in the range of approximately 1 to 1.6 inches. Finally, sample size was

considered. The specification for the National Standard for Spatial Data Accuracy is a minimum of 20 points to conduct a statistically

significant accuracy evaluation (Minnesota Planning, 1999, Positional Accuracy Handbook, Minnesota Planning Land Management Information Center,

St. Paul, Minnesota., p.3). Most statistical texts indicate that a minimum of 30 sample points provide a reasonable Approximation of a normal

distribution. The intent of the NSSDA is to reflect the geographic area of interest and the distribution of error in the data set

(Federal Geographic Data Committee, 1998, Geospatial National Standard for Spatial Data Accuracy, Federal Geographic Data Committee Secretariat,

Reston, Virginia, p.3-4). Additional steps were taken to ensure the vertical accuracy of the LiDAR data including:

Step 1: Precision Bore sighting (Check Edge-matching);

Step 2: Compare the LiDAR data to the Field Survey (Field survey is to FEMA specifications and more stringent internal specifications);

Step 3: Automated Filtering;

Step 4: Manual Editing (Quality Control) Step

; Quantitative Value: 0.15 meters, Test that produced the value: See entity and attribute information

Cloud Cover: 0

The LAS files were flown at a density sufficient to support a maximum final post spacing of final post spacing of 1.5 points per meter.

The Light Detection and Ranging (LiDAR) LAS dataset is a topographic survey conducted for the Post Hurricane Gustav and Post Hurricane Ike Aerial

Survey Projects. These data were produced for the US Army Corps of Engineers (USACE) Joint Airborne Lidar Bathymetry Technical Center of

Expertise (JALBTCX).