Topographic Lidar Survey of the Chandeleur Islands, Louisiana, February 6, 2012 -- Bare Earth DEMs

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Frequently anticipated questions:

What does this data set describe?

Title:
Topographic Lidar Survey of the Chandeleur Islands, Louisiana, February 6, 2012 -- Bare Earth DEMs
Abstract:
A topographic Lidar survey was conducted on February 6, 2012, over the Chandeleur Islands, Louisiana. The data were collected at a nominal pulse space of 0.5-meter (m) and processed to identify bare earth elevations. Bare earth digital elevation models (DEMs) were generated based on these data. Digital Aerial Solutions, LLC, 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 in decimal degree geographic coordinates, North American Datum 1983, National Spatial Reference System 2007 (NAD83 NSRS2007)). Their vertical datum is North American Vertical Datum 1988, Geoid 2009, Geodetic Reference System 1980 (NAVD88 GEOID09 GRS80) in meters. Thirty-three DEMs, based on a 2-kilometer (km) by 2-km tiling scheme, cover 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 Digital Aerial Solutions, LLC. Digital Aerial Solutions was contracted by the U.S. Geological Survey to conduct the work. Each tile is 2000 m by 2000 m in size, based on UTM Zone 16N NAD83 meters. The extent of each tile falls on even 1000 x and y UTM Zone 16N NAD83 coordinates. Tile names are assigned according to the U.S. National Grid (USNG) spatial address (http://www.fgdc.gov/usng/how-to-read-usng/index_html). The last 4 digits of the file name are based on the lower-left (LL) xy coordinate of the tile. For example, tile name 16RCU2304 uses 23 to represent an LL x-coordinate of 323,000 (ignoring the first digit), and uses 04 to represent an LL y-coordinate of 3,304,000 (ignoring the first two digits).
  1. How might this data set be cited?
    U.S. Geological Survey, 20131115, Topographic Lidar Survey of the Chandeleur Islands, Louisiana, February 6, 2012 -- Bare Earth DEMs: U.S. Geological Survey Data Series 840, U.S. Geological Survey, St. Petersburg, Fla..

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -88.9137598
    East_Bounding_Coordinate: -88.8113368
    North_Bounding_Coordinate: 30.0342555
    South_Bounding_Coordinate: 29.7444381
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Calendar_Date: 06-Feb-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 Point data set. It contains the following vector data types (SDTS terminology):
      • Point
    2. What coordinate system is used to represent geographic features?
      The horizontal datum used is North American Datum of 1983 (NSRS2007).
      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 (GEOID09)
      Altitude_Resolution: 0.00001
      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, 32-bit floating point continuous rasters in ERDAS Imagine format derived from bare earth classified lidar data. The vertical units are in meters, NAVD88, GEOID09.
    Entity_and_Attribute_Detail_Citation:
    USGS. 2013. Topographic Lidar Survey Chandeleur Islands, Louisiana, February 6, 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. The U.S. Geological Survey staff would also appreciate it if those products were shared with them. 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.
  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

    727-502-8000 (voice)
    727-502-8001 (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 short- and long-term changes of several different barrier island systems. Specifically, this survey supports detailed studies of the Chandeleur Islands that resolve annual changes in beaches, berms and dunes associated with processes driven by storms, sea-level rise, and 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)
    Digital Aerial Solutions, LLC., 2012, RAW Lidar Data.

    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.
    Ground Control Points (source 2 of 2)
    U.S. Geological Survey, 2012, Ground Control Points.

    Type_of_Source_Media: online
    Source_Contribution:
    This data source was used in Lidar processing and accuracy assessment. This dataset is not included in this data series.
  2. How were the data generated, processed, and modified?
    Date: 2012 (process 1 of 7)
    The airborne global positioning system (ABGPS), inertial measurement units (IMU), and raw ALS60 Lidar data were integrated into the Leica post processor software. The resultant file is in a LAS binary file format. The LAS file version 1.2 format can be easily transferred from one file format to another. It is a binary file format that maintains information specific to the Lidar data (return number, intensity value, xyz, etc.). The resultant points are produced in the geodetic coordinates referenced to the vertical datum. The ABGPS, IMU and raw Lidar data are intermediary datasets and are not included in this data series. Person who carried out this activity:
    Digital Aerial Solutions, LLC.
    8409 Laurel Fair Circle Suite 100
    Tampa, FL
    USA

    813-628-0788 (voice)
    813-628-0777 (FAX)
    Hours_of_Service: Monday through Friday 8:00 AM to 5:00 PM (Eastern Time)
    Data sources used in this process:
    • Raw Lidar Data
    Data sources produced in this process:
    • Calibrated Lidar Datasets
    Date: 2012 (process 2 of 7)
    The unedited data were classified to facilitate the application of the appropriate feature extraction filters. A combination of proprietary filters was applied as appropriate for the production of bare earth Digital Terrain Models (DTMs). Interactive editing methods were applied to those areas where it was inappropriate or impossible to use the feature extraction filters, based upon the design criteria and/or limitations of the relevant filters. These same feature extraction filters were used to produce elevation height surfaces. The Lidar mass points are in American Society for Photogrammetry and Remote Sensing (ASPRS) LAS 1.2 format. The header file for each dataset is complete as defined by the LAS 1.2 specification. The data was classified as follows: Classes 1 and 17 = Unclassified. Class 2 = Ground. Class 9 = Water. Class 10 = Breakline Proximity. Person who carried out this activity:
    Digital Aerial Solutions, LLC.
    Attn: Joshua Helton
    Director Lidar Programs
    8409 Laurel Fair Circle Suite 100
    Tampa, FL
    USA

    813-628-0788 (voice)
    813-628-0777 (FAX)
    jhelton@digitalaerial.com
    Hours_of_Service: Monday through Friday 8:00 AM to 5:00 PM (Eastern Time)
    Data sources used in this process:
    • Calibrated Lidar Datasets
    Data sources produced in this process:
    • Classified Lidar Datasets
    Date: 2012 (process 3 of 7)
    The Spatial Reference Geographic (latitude and longitude) decimal degrees NAD83 coordinates were converted from ellipsoid heights (m) into orthometric heights using NAVD88 (m). The files were orthogonally tiled based on a 2000 m x 2000 m extent, and labeled with a "Tile_ID" attribute. Person who carried out this activity:
    Digital Aerial Solutions, LLC.
    Attn: Joshua Helton
    Director Lidar Programs
    8409 Laurel Fair Circle Suite 100
    Tampa, FL
    USA

    813-628-0788 (voice)
    813-628-0777 (FAX)
    jhelton@digitalaerial.com
    Hours_of_Service: Monday through Friday 8:00 AM to 5:00 PM (Eastern Time)
    Data sources used in this process:
    • Classified Lidar Datasets
    Data sources produced in this process:
    • Tiled Orthometric Lidar Datasets
    Date: 2012 (process 4 of 7)
    Breakline collection was done in order to create hydro-flattened Digital Elevation Models. Breaklines were collected for streams, rivers, and inland water bodies and visually inspected. Elevation from the Lidar point cloud is used to derive a static elevation for hydro flattening. Person who carried out this activity:
    Digital Aerial Solutions, LLC.
    Attn: Joshua Helton
    Director Lidar Programs
    8409 Laurel Fair Circle Suite 100
    Tampa, FL
    USA

    813-628-0788 (voice)
    813-628-0777 (FAX)
    jhelton@digitalaerial.com
    Hours_of_Service: Monday through Friday 8:00 AM to 5:00 PM (Eastern Time)
    Data sources used in this process:
    • Classified Lidar datasets
    Data sources produced in this process:
    • Hydro Breaklines
    Date: 2012 (process 5 of 7)
    The digital elevation models (DEMs) were derived from the classified lidar point cloud using ArcMap extension LP360. The DEMs are 32-bit floating point ERDAS Imagine IMG files with a cell size of less-than or equal to 1 m. All inland water bodies, streams, and rivers that were non-tidal water bodies were hydro-flattened within each DEM. The vertical accuracy of DEMs were assessed using methods adopted by the ASPRS National Digital Elevation Program (NDEP) for fundamental vertical accuracy (FVA) and consolidated vertical accuracy CVA. Person who carried out this activity:
    Digital Aerial Solutions, LLC
    Attn: Joshua Helton
    Director Lidar Programs
    8409 Laurel Fair Circle Suite 100
    Tampa, FL
    USA

    (813) 628-0788 (voice)
    (813) 628-0777 (FAX)
    jhelton@digitalaerial.com
    Hours_of_Service: 8:00 - 5:00 Eastern
    Data sources used in this process:
    • Classified Lidar datasets
    • Hydro Breaklines
    • Ground Control Points
    Data sources produced in this process:
    • Hydro Enforced Raster DEMs
    Date: 04-Jan-2017 (process 6 of 7)
    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 7 of 7)
    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?
    Lidar data horizontal accuracy was tested to meet a 1.0 m root mean square error (RMSEz) or less.
  3. How accurate are the heights or depths?
    Lidar vertical data accuracy determination used the National Standard for Spatial Data Accuracy (NSSDA). The contract specified a 15 centimeter (cm) (RMSEz) or better on open bare terrain and a 43.6 cm (RMSEz) or better in vegetative areas.
  4. Where are the gaps in the data? What is missing?
    The data was visually inspected for completeness.
  5. How consistent are the relationships among the observations, including topology?
    Bare-earth processed data for this acquisition block comply with the following accuracy requirements for Artifact/Feature removal: artifacts - 90 percent; outliers - 95 percent; vegetation - 95 percent; buildings - 98 percent. 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 the correct physical format and is readable.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?
Access_Constraints: No restrictions apply to these data.
Use_Constraints:
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 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.
  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

    727-502-8000 (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 840
  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: ERDAS Imagine IMG, zipped
      Network links: http://pubs.usgs.gov/ds/0840/
    • 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

727-502-8000 (voice)
727-502-8001 (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-840_DEM_Topographic_Lidar_Survey_Feb_2012.faq.html>
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