Topographic Lidar Survey of the Alabama, Mississippi, and Southeast Louisiana Barrier Islands, from September 5 to October 11, 2012 -- Bare Earth Digital Elevation Models

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Frequently anticipated questions:

What does this data set describe?

Title:
Topographic Lidar Survey of the Alabama, Mississippi, and Southeast Louisiana Barrier Islands, from September 5 to October 11, 2012 -- Bare Earth Digital Elevation Models
Abstract:
A topographic lidar survey was conducted from September 5 to October 11, 2012, for the barrier islands of Alabama, Mississippi and southeast Louisiana, including the coast near Port Fourchon. Most of the data were collected September 5-10, 2012, with a reflight conducted on October 11, 2012, to increase point density in some areas. The data were collected at a nominal pulse space of 1-meter (m) and processed to identify bare earth elevations. Bare earth Digital Elevation Models(DEMs) were generated based on these data. Aero-Metric, Inc., was contracted by the U.S. Geological Survey (USGS) to collect and process the lidar data. The bare earth DEMs are 32-bit floating point ERDAS Imagine (IMG) files with a horizontal spatial resolution of 1-m by 1-m. They are projected to UTM zone 15N or 16N NAD83 meters. Their vertical datum is NAVD88 (GEOID12) meters. The DEMs are organized on a 2-kilometer (km) by 2-km tiling scheme that covers the entire survey area. These lidar data are available to Federal, State and local governments, emergency-response officials, resource managers, and the general public.
Supplemental_Information:
Lidar data acquisition, calibration, and follow-on processing were completed by Aero-Metric, Inc. Aero-Metric was contracted by the USGS to conduct the work. The file naming convention is based on a 2-km by 2-km tiling scheme. The geographic extent of each tile falls on even 2000 x and y coordinates in UTM zone 15N or 16N, NAD83, meters. The first two digits of the file name represent the UTM zone. The last eight digits are based on the lower-left (LL) xy coordinate of the tile. For example, tile name 15_69802160 uses 6980 to represent an LL x-coordinate of 698,000, and uses 2160 to represent an LL y-coordinate of 3,216,000 (ignoring the first digit).
  1. How might this data set be cited?
    U.S. Geological Survey, 2013, Topographic Lidar Survey of the Alabama, Mississippi, and Southeast Louisiana Barrier Islands, from September 5 to October 11, 2012 -- Bare Earth Digital Elevation Models: U.S. Geological Survey Data Series 839, U.S. Geological Survey, St. Petersburg, Fla..

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -90.975
    East_Bounding_Coordinate: -88.055
    North_Bounding_Coordinate: 30.266
    South_Bounding_Coordinate: 29.020
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 05-Sep-2012
    Ending_Date: 11-Oct-2012
    Currentness_Reference:
    ground condition
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: remote-sensing image
  6. How does the data set represent geographic features?
    1. How are geographic features stored in the data set?
      Indirect_Spatial_Reference: Tile Index
      This is a Raster data set. It contains the following raster data types:
      • Dimensions, type Pixel
    2. What coordinate system is used to represent geographic features?
      Grid_Coordinate_System_Name: Universal Transverse Mercator
      Universal_Transverse_Mercator:
      UTM_Zone_Number: 16
      Transverse_Mercator:
      Scale_Factor_at_Central_Meridian: 0.9996
      Longitude_of_Central_Meridian: -87.000000
      Latitude_of_Projection_Origin: 0.0
      False_Easting: 500000
      False_Northing: 0.0
      Planar coordinates are encoded using coordinate pair
      Abscissae (x-coordinates) are specified to the nearest 0.01
      Ordinates (y-coordinates) are specified to the nearest 0.01
      Planar coordinates are specified in meters
      The horizontal datum used is North American Datum of 1983.
      The ellipsoid used is Geodetic Reference System 80.
      The semi-major axis of the ellipsoid used is 6378137.
      The flattening of the ellipsoid used is 1/298.257222101.
      Vertical_Coordinate_System_Definition:
      Altitude_System_Definition:
      Altitude_Datum_Name: North American Vertical Datum of 1988
      Altitude_Resolution: 0.01
      Altitude_Distance_Units: meters
      Altitude_Encoding_Method:
      Explicit elevation coordinate included with horizontal coordinates
  7. How does the data set describe geographic features?
    Entity_and_Attribute_Overview:
    The bare earth DEMs are composed of single band, 1-m by 1-m resolution, 32-bit floating point continuous rasters in ERDAS Imagine format derived from bare earth classified lidar data. The vertical units are in meters, NAVD88, GEOID12.
    Entity_and_Attribute_Detail_Citation:
    USGS. 2013. Topographic Lidar Survey of the Alabama, Mississippi and Southeast Louisiana Barrier Islands, September 5 to October 11, 2012.

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • U.S. Geological Survey
  2. Who also contributed to the data set?
    Acknowledgment of the U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center, as a data source would be appreciated in products developed from these data, and such acknowledgment as is standard for citation and legal practices. Sharing of new data layers developed directly from these data would also be appreciated by the U.S. Geological Survey staff. Users should be aware that comparisons with other datasets for the same area from other time periods may be inaccurate due to inconsistencies resulting from changes in photointerpretation, mapping conventions, and digital processes over time. These data are not legal documents and are not to be used as such. Native_Dataset_Environment: Contractor: Aero-Metric, Inc.; 1. Scanner - Optech 3100 Serial 05SEN175 and Leica ALS70 SN7169; 2. Processing Programs and versions - Applanix - POSGPS and POSProc, versions 4.4, MMS version 5.2; 3. Program and version - Optech ASDA; 4. Processing Programs and versions - TerraSolid TerraScan (version 012.016), TerraModeler (version 012.008) and TerraMatch (version 012.009), Intergraph MicroStation (version 08.05.02.55), and GeoCue (version 2011.1.20.4).; 5. Viewing Program - GlobalMapper V13.00
  3. To whom should users address questions about the data?
    U.S. Geological Survey
    Attn: Nathaniel Plant
    600 4th St. S.
    St. Petersburg, FL
    USA

    727-803-8747 (voice)
    727-803-2031 (FAX)
    nplant@usgs.gov
    Hours_of_Service: Monday through Friday 9:00 AM to 5:00 PM (Eastern Time)

Why was the data set created?

This lidar survey was acquired to document the change of several different barrier island systems resulting from Hurricane Isaac. The survey supports detailed studies of Louisiana, Mississippi and Alabama barrier islands that resolve annual and episodic changes in beaches, berms and dunes associated with processes driven by storms, sea-level rise, and even human restoration activities.

How was the data set created?

  1. From what previous works were the data drawn?
    Raw Lidar Data (source 1 of 2)
    Aero-Metric, Inc., 20130124, Lidar RAW Data for Gulf of Mexico Barrier Islands: Aero-Metric, Inc. Aerial LiDAR Department, Aero-Metric, Inc..

    Type_of_Source_Media: digital hard drive
    Source_Contribution:
    This data source was used to populate the lidar point cloud data. This dataset is not included in this Data Series Report.
    Ground Control Points (source 2 of 2)
    U.S. Geological Survey, 2012, Ground Control Points.

    Type_of_Source_Media: digital hard drive
    Source_Contribution:
    This data source was used in lidar processing and accuracy assessment. This dataset is not included in this Data Series Report.
  2. How were the data generated, processed, and modified?
    Date: 01-Oct-2012 (process 1 of 5)
    Lidar Pre-Processing: The point cloud data was imported to TerraScan in a Microstation V8 (V) CAD environment on a specified 2000 m by 2000 m tiling scheme. The data were analyzed for overall completeness and consistency. The data were then inspected for calibration errors with TerraMatch software.
    Date: 01-Oct-2012 (process 2 of 5)
    Lidar Ground Classification: Automatic ground classification was performed using algorithms with customized parameters to best fit the project area. Areas of varying relief and planimetric features were inspected to verify the ground classification. Each tile was reviewed for accuracy and consistency. Person who carried out this activity:
    Aero-Metric, Inc.
    4020 Technology Parkway
    Sheboygan, WI
    USA

    920-457-3631 (voice)
    920-457-4010 (FAX)
    Data sources used in this process:
    • Calibrated Lidar Datasets
    Data sources produced in this process:
    • Classified Lidar Datasets
    Date: 01-Oct-2012 (process 3 of 5)
    The bare earth lidar points were used to generate ASCII formatted DEMs. The DEMs were reviewed for completeness and adherence to the tile layout used during creation. The files were converted to IMG format with ArcMap. Person who carried out this activity:
    Aero-Metric, Inc.
    4020 Technology Parkway
    Sheboygan, WI
    USA

    920-457-3631 (voice)
    920-457-4010 (FAX)
    Data sources used in this process:
    • Classified Lidar Datasets
    Data sources produced in this process:
    • Raster DEMs
    Date: 04-Jan-2017 (process 4 of 5)
    Keywords section of metadata optimized for discovery in USGS Coastal and Marine Geology Data Catalog. Person who carried out this activity:
    U.S. Geological Survey
    Attn: Alan O. Allwardt
    Contractor -- Information Specialist
    2885 Mission Street
    Santa Cruz, CA

    831-460-7551 (voice)
    831-427-4748 (FAX)
    aallwardt@usgs.gov
    Date: 13-Oct-2020 (process 5 of 5)
    Added keywords section with USGS persistent identifier as theme keyword. Person who carried out this activity:
    U.S. Geological Survey
    Attn: VeeAnn A. Cross
    Marine Geologist
    384 Woods Hole Road
    Woods Hole, MA

    508-548-8700 x2251 (voice)
    508-457-2310 (FAX)
    vatnipp@usgs.gov
  3. What similar or related data should the user be aware of?

How reliable are the data; what problems remain in the data set?

  1. How well have the observations been checked?
  2. How accurate are the geographic locations?
    Area data products collected with the Optech 3100 or Leica ALS70 were acquired at or below 1200 m above mean terrain (AMT) and have a horizontal accuracy of 0.218 m (per manufacturers system specifications), with a nominal point spacing of 1.0 m.
  3. How accurate are the heights or depths?
    The USGS conducted ground surveys in a small area on Chandeleur Island on September 6, 2012, one on bare earth and another in mixed bare earth and vegetated areas. The USGS calculated a vertical root mean square error (RMSEz) of 0.072 m and an offset of 0.007 m using interpolated 2-m by 2-m resolution grid surfaces made from lidar bare-earth data and combined USGS ground surveys. The contractor was required to achieve a fundamental vertical accuracy (FVA) of 24.5 centimeters (cm), 95 percent (12.5 cm RMSEz); a consolidated vertical accuracy (CVA) of 36.3 cm, 95th percentile; and a target value for supplemental vertical accuracies (SVA) of 36.3 cm, 95th percentile. Aero-Metric's vertical accuracy assessment was as follows: The FVA of the LAS Swath Data achieved 5.0 cm at a 95 percent confidence level with an RMSE of 2.5 cm utilizing (2280) ground survey check points provided by the USGS. The SVA results in an area of open terrain achieved 4.8 cm at the 95th percentile where (2280) ground survey check points provided by the USGS were evaluated. The SVA results in an area of vegetation achieved 10.7 cm at the 95th percentile where (2421) ground survey check points provided by the USGS were evaluated. The CVA results for all land cover classes, ground and vegetation combined, achieved 7.3 cm at the 95th percentile where (4700) checkpoints were evaluated. The USGS also conducted a terrestrial lidar survey on Dauphin Island, Louisiana, on September 3, 2012. The USGS calculated an RMSEz of 0.32 m and an offset of 0.27 m using interpolated 2-m by 2-m resolution grid surfaces from the airborne lidar bare-earth data and the terrestrial lidar survey.
  4. Where are the gaps in the data? What is missing?
    Complete.
  5. How consistent are the relationships among the observations, including topology?
    The classified lidar data exchange format (LAS) files were tested by Aero-Metric for vertical and horizontal accuracy.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?
Access_Constraints: None.
Use_Constraints:
None. However, users should be aware that temporal changes may have occurred since this dataset was collected and some parts of this data may no longer represent surface conditions. Users should not use this data for critical applications without a full awareness of its limitations. Acknowledgment of the U.S. Geological Survey would be appreciated for products derived from these data.
  1. Who distributes the data set? (Distributor 1 of 1)
    Nathaniel Plant
    U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center, St. Petersburg, Fla.
    Research Oceanographer
    600 4th Street South
    St. Petersburg, FL
    USA

    727-803-8747 (voice)
    Hours_of_Service: Monday-Friday, 9:00-5:00 Eastern Time
  2. What's the catalog number I need to order this data set? DS 839
  3. What legal disclaimers am I supposed to read?
    Although these data were processed successfully on a computer system at the USGS, no warranty expressed or implied is made regarding the display or utility of the data on any other system, or for general or scientific purposes, nor shall the act of distribution constitute any such warranty. The USGS shall not be held liable for improper or incorrect use of the data described and/or contained herein. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
  4. How can I download or order the data?
    • Availability in digital form:
      Data format: LAS, zipped
      Network links: http://pubs.usgs.gov/ds/0839/
    • Cost to order the data: None if obtained online; otherwise prices vary.

    • Special instructions:
      Publications are available from USGS Information Services, Box 25286, Federal Center, Denver, CO 80225-0046 (telephone: 1-888-ASK-USGS, e-mail: infoservices@usgs.gov).

Who wrote the metadata?

Dates:
Last modified: 13-Oct-2020
Metadata author:
U.S. Geological Survey
Attn: K. Guy
600 4th Street South
St. Petersburg, FL
USA

727-803-8747 (voice)
727-803-2031 (FAX)
kguy@usgs.gov
Hours_of_Service: Monday through Friday 9:00 AM to 5:00 PM (Eastern Time)
Metadata standard:
FGDC Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)
This page is <https://cmgds.marine.usgs.gov/catalog/spcmsc/metadata_DS-839_DEM_Topographic_Lidar_Survey_Sept-Oct_2012.faq.html>
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