Topobathymetric Lidar Survey of Breton and Gosier Islands, Louisiana, January 16 and 18, 2014

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Frequently anticipated questions:


What does this data set describe?

Title:
Topobathymetric Lidar Survey of Breton and Gosier Islands, Louisiana, January 16 and 18, 2014
Abstract:
This dataset contains binary point-cloud data and a Digital Elevation Model (DEM), produced from remotely sensed, geographically referenced topobathymetric measurements collected by Photo Science, Inc., encompassing the Breton Island, LA study area. The original area of interest was buffered by 100 meters to ensure complete coverage, resulting in approximately 75 square miles of lidar data. The Breton Island Lidar project called for the planning, acquisition, processing, and derivative products of topobathymetric lidar data, collected at a nominal pulse spacing (NPS) of 0.5-0.45 meters (4-5 points/square meter). Lidar acquisition was prioritized to coincide with the lowest tide possible. Water clarity was also assessed and deemed acceptable prior to acquisition flights. The data, in meters, are projected to UTM Zone 16 North and referenced horizontally to the NAD83 (2011) datum and vertically to the NAVD88 (GEOID12A) datum. The classified point-cloud data were delivered in LAS v1.2 format and the merged DEM was converted to a GeoTIFF file. Each LAS file contains data in a 1-kilometer by 1-kilometer tile named according to the US National Grid conventions.
  1. How might this data set be cited?
    Terrano, Joseph F., Flocks, James G., and Smith, Kathryn E., 20160325, Topobathymetric Lidar Survey of Breton and Gosier Islands, Louisiana, January 16 and 18, 2014: U.S. Geological Survey Data Release doi:10.5066/F70G3H6G, U.S. Geological Survey, St. Petersburg, FL.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -89.19718926
    East_Bounding_Coordinate: -89.16698352
    North_Bounding_Coordinate: 29.49840292
    South_Bounding_Coordinate: 29.46161963
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Calendar_Date: 16-Jan-2014
    Currentness_Reference:
    ground condition
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: lidar point cloud (Digital Elevation Model)
  6. How does the data set represent geographic features?
    1. How are geographic features stored in the data set?
      This is a Point 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: 0.999600
      Longitude_of_Central_Meridian: -87.000000
      Latitude_of_Projection_Origin: 0
      False_Easting: 500000.000000
      False_Northing: 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 6378137.000000.
      The flattening of the ellipsoid used is 1/298.25722210100002.
      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?

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • Joseph F. Terrano
    • James G. Flocks
    • Kathryn E. Smith
  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.
  3. To whom should users address questions about the data?
    Joseph F. Terrano
    U.S. Geological Survey Coastal and Marine Science Center, St. Petersburg, FL, Contracted through Cherokee Nation Technology
    Researcher 1
    600 4th Street South
    St. Petersburg, FL
    USA

    727-502-8047 (voice)
    727-502-8182 (FAX)
    jterrano@usgs.gov
    Hours_of_Service: M-F, 9:00-5:00 ET

Why was the data set created?

Lidar data were acquired to document the short and long-term changes of several barrier island systems in Louisiana. Digitized shorelines created from the Lidar data provide an accurate and measurable change in shape, area, and shoreline movement over short and long-term periods. Lidar, in the form of a Digital Elevation Models, can provide a measurable change in the topography of barrier island systems to track pre- and post- storm elevation changes.

How was the data set created?

  1. From what previous works were the data drawn?
  2. How were the data generated, processed, and modified?
    Date: 2014 (process 1 of 2)
    Quantum Spatial provided the following steps: Lidar Pre-Processing: 1. Flight lines and data were reviewed to ensure complete coverage of the study area and positional accuracy of the laser points. 2. Resolved kinematic corrections for aircraft position data using kinematic aircraft GPS and static ground GPS data. 3. Developed a smoothed best estimate of trajectory (SBET) file that blended post-processed aircraft position with attitude data. Sensor head position and attitude were calculated throughout the survey. The SBET data were used extensively for laser point processing. 4. Calculated laser point position by associating SBET position to each laser point return time, scan angle, intensity, etc. Data were converted to orthometric elevations (NAVD88) by applying a Geoid12a correction. 5. Filtered out erroneous points. 6. Performed automated line-to-line calibrations for system attitude parameters (pitch, roll, heading), mirror flex (scale) and GPS/IMU drift. Calibrations were calculated on matching surfaces within and between each line and results were applied to all points in a flight line. Every flight line was used for relative accuracy calibration. 7. Identified and refracted all returns requiring a refraction correction. 8. Assessed statistical absolute accuracy via direct comparisons of surface points to ground survey data. Data were exported to standard LAS 1.2 format. Person who carried out this activity:
    Quantum Spatial/USGS
    Geospatial Services
    600 4th St. South
    St. Petersburg, FL
    USA

    727-502-8047 (voice)
    727-502-8182 (FAX)
    Hours_of_Service: Monday through Friday 8:00 AM to 5:00 PM (Eastern Time)
    Date: 2014 (process 2 of 2)
    Quantum Spatial provided the following steps: Lidar Post-Processing: The calibrated and controlled lidar swaths were processed using proprietary automated point classification routines. These routines operate against the entire collection (all swaths, all lifts), eliminating character differences between files. Data were then distributed as virtual tiles to experienced lidar analysts for localized automatic classification, manual editing, and peer-based quality control (QC) checks. Supervisory QC monitoring of work in progress and completed editing ensured consistency of classification character and adherence to project requirements across the entire project area. Person who carried out this activity:
    Quantum Spatial/USGS
    Geospatial Services
    600 4th St. South
    St. Petersburg, FL
    USA

    727-502-8047 (voice)
    727-502-8182 (FAX)
    Hours_of_Service: Monday through Friday 8:00 AM to 5:00 PM (Eastern Time)
  3. What similar or related data should the user be aware of?
    Joseph F. Terrano, James G. Flocks, and Kathryn E.L. Smith, 20151203, A GIS Compilation of Vector Shorelines and Associated Shoreline Change Data for Breton Island, Louisiana: 1869-2014: U.S. Geological Survey Data Release doi-F7XS5SGM, U.S. Geological Survey, St. Petersburg, FL.

    Online Links:

    Joseph F. Terrano, James G. Flocks, and Kathryn E.L. Smith, Unpublished, Analysis of Shoreline and Geomorphic Change for Breton Island, Louisiana from 1869 to 2014: U.S. Geological Survey Open File Report Unpublished, U.S. Geological Survey, St. Petersburg, FL.

    Online Links:

    • To be determined


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?
    Horizontal accuracy details were not included in the report provided by Photo Science, Inc.
  3. How accurate are the heights or depths?
    The fundamental and vertical accuracy was tested with 10 bare earth ground control points provided by the USGS. The survey checkpoints were distributed throughout the project area, where appropriate. The Root Mean Square Error (RMSE) of the vertical accuracy of this dataset is 0.03 meters. Additionally, a few ground control points were provided by the USGS in various land cover types. The land classes and number of control points are as follows: Mangroves (1), Short Grass (1), Tall Grass (1), Submerged (4), and Surf Zone (3). Despite the small sample sizes, supplemental vertical accuracy of each land cover type was calculated. All points (bare earth and land cover) were used to calculate the classified vertical accuracy. 0.060 meters Accuracy(z) at 95 percent confidence interval. Fundamental Vertical Accuracy (FVA) was assessed using 10 ground survey points provided by USGS. Elevations from the unclassified lidar surface were measured for the x,y location of each check point. Elevations interpolated from the lidar surface were then compared to the elevation values of the surveyed control. The RMSE was computed to be 0.06 m. Accuracy(z) has been tested to meet 24.5 cm FVA at 95 Percent confidence level using RMSE(z) x 1.9600 as defined by the National Standards for Spatial Data Accuracy (NSSDA); assessed and reported using National Digital Elevation Program (NDEP)/ASRPS Guidelines.
  4. Where are the gaps in the data? What is missing?
    Datasets contain complete coverage of tiles.A visual qualitative assessment was performed to ensure data completeness. The raw point cloud is of good quality and data passes Fundamental Vertical Accuracy specifications.
  5. How consistent are the relationships among the observations, including topology?
    "No Data" values are a result of the survey not covering the particular region, areas of turbid water, or the manual removal of lidar processing artifacts.

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:
The U.S. Geological Survey requests to be acknowledged as originator of these data in future products or derivative research.
  1. Who distributes the data set? (Distributor 1 of 1)
    U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center, St. Petersburg, FL
    Attn: Joseph F. Terrano
    Researcher 1
    600 4th Street South
    St. Petersburg, FL
    USA

    (727)502-5047 (voice)
    Hours_of_Service: M-F, 9:00-5:00 ET
  2. What's the catalog number I need to order this data set? Breton_Island_2014_DEM
  3. What legal disclaimers am I supposed to read?
    Although these data have been 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?

Who wrote the metadata?

Dates:
Last modified: 25-Mar-2016
Metadata author:
Joseph F. Terrano
Researcher 1
600 4th Street South
St. Petersburg, FL
USA

727 502-8047 (voice)
jterrano@usgs.gov
Hours_of_Service: M-F, 9:00-5:00 ET
Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)

This page is <https://cmgds.marine.usgs.gov/catalog/spcmsc/Breton_Island_2014_DEM_metadata.faq.html>
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