Uncalibrated EAARL-B Submerged Topography--Fort Lauderdale, Florida, 2014 (WGS84)

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Frequently anticipated questions:

What does this data set describe?

Uncalibrated EAARL-B Submerged Topography--Fort Lauderdale, Florida, 2014 (WGS84)
Binary point-cloud data of a portion of the submerged environs of Fort Lauderdale, Florida, were produced from remotely sensed, geographically referenced elevation measurements by the U.S. Geological Survey (USGS). Elevation measurements were collected over the area using the second-generation Experimental Advanced Airborne Research Lidar (EAARL-B), a pulsed laser ranging system mounted onboard an aircraft to measure ground elevation, vegetation canopy, and coastal topography. The system uses high-frequency laser beams directed at the Earth's surface through an opening in the bottom of the aircraft's fuselage. The laser system records the time difference between emission of the laser pulse and the reception of the reflected laser signal in the aircraft. The plane travels over the target area at approximately 60 meters per second at an elevation of approximately 300 meters, resulting in a laser swath of approximately 240 meters with an average point spacing of 0.5-1.6 meters. The EAARL, developed originally by the National Aeronautics and Space Administration (NASA) at Wallops Flight Facility in Virginia, measures ground elevation with a vertical resolution of 3 centimeters. A peak sampling rate of 15-30 kilohertz results in an extremely dense spatial elevation dataset. Over 100 kilometers of coastline can be surveyed easily within a 3- to 4-hour mission. When resultant elevation maps for an area are analyzed, they provide a useful tool to make management decisions regarding land development.
Raw lidar data are not in a format that is Nonely usable by resource managers and scientists for scientific analysis. Converting dense lidar elevation data into a readily usable format without loss of essential information requires specialized processing. The USGS's Coastal and Marine Geology Program (CMGP) has developed custom software to convert raw lidar data into a GIS-compatible map product to be provided to GIS specialists, managers, and scientists. The primary tool used in the conversion process is Airborne Lidar Processing System (ALPS), a multi-tiered processing system developed originally by a USGS-NASA collaborative project. Specialized processing algorithms are used to convert raw waveform lidar data acquired by the EAARL-B to georeferenced spot (x,y,z) returns for "first surface" and "bare earth" topography. The terms first surface and bare earth refer to the digital elevation data of the terrain, but while first-surface data include vegetation, buildings, and other manmade structures, bare-earth data do not. The zero crossing of the second derivative (that is, detection of stationary points) is used to detect the first return, resulting in "first surface" topography, while the trailing edge algorithm (that is, the algorithm searches for the location prior to the last return where direction changes along the trailing edge) is used to detect the range to the last return, or "bare earth" (the first and last returns being the first and last significant measurable portion of the return pulse). First and last returns, in the context of submerged topography data, produce an elevation map of the surface of the water and the seafloor, respectively. Statistical filtering, known as the Random Consensus Filter (RCF), is used to remove false bottom returns and other outliers from the EAARL-B topography data. The filter uses a grid of square cells (buffer) of user-defined size overlaid onto the original point cloud. The user also defines the vertical tolerance (vertical width) based on the topographic complexity and point-sampling density of the data. The maximum allowable elevation range within a cell is established by this vertical tolerance. An iterative process searches for the maximum concentration of points within the vertical tolerance and removes those points outside of the tolerance (Nayegandhi and others, 2009). Please note that these data are not suitable for navigational use, nor for determining absolute elevation measurements. Submerged topography was assigned to Class 29.
  1. How might this data set be cited?
    Kranenburg, Christine J., Wright, C. Wayne, and Klipp, Emily S., 20160510, Uncalibrated EAARL-B Submerged Topography--Fort Lauderdale, Florida, 2014 (WGS84): U.S. Geological Survey Data Release doi:10.5066/F79S1P4S, U.S. Geological Survey, St. Petersburg, FL.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -80.1213
    East_Bounding_Coordinate: -80.0848
    North_Bounding_Coordinate: 25.9821
    South_Bounding_Coordinate: 25.9097
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Calendar_Date: 21-Apr-2014
    ground condition
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: vector digital data
  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.
    2. What coordinate system is used to represent geographic features?
      Grid_Coordinate_System_Name: Universal Transverse Mercator
      UTM_Zone_Number: 17
      Scale_Factor_at_Central_Meridian: 0.999600
      Longitude_of_Central_Meridian: -81.000000
      Latitude_of_Projection_Origin: 0.000000
      False_Easting: 500000.000000
      False_Northing: 0.000000
      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 World Geodetic System 1984 (G1674).
      The ellipsoid used is WGS_1984.
      The semi-major axis of the ellipsoid used is 6378137.000000.
      The flattening of the ellipsoid used is 1/298.257223563.
      Altitude_Datum_Name: World Geodetic System 1984
      Altitude_Resolution: 0.01
      Altitude_Distance_Units: meters
      Explicit elevation coordinate included with horizontal coordinates
  7. How does the data set describe geographic features?
    This file consists of uncalibrated submerged topography elevation data available for this survey. Data were processed via using ALPS software. Data were quality controlled through the application of the RCF, manual editing in ALPS, and inspection in Global Mapper. Submerged topography was assigned to Class 29.
    Entity_and_Attribute_Detail_Citation: http://pubs.usgs.gov/of/2009/1078/

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • Christine J. Kranenburg
    • C. Wayne Wright
    • Emily S. Klipp
  2. Who also contributed to the data set?
    Acknowledgment of the USGS, 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 for data source is expected by users of this data. Sharing of new data layers developed directly from these data would also be appreciated by the USGS 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?
    Christine Kranenburg
    Cherokee Nation Technologies, U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center, St. Petersburg, FL
    Computer Scientist
    600 4th Street South
    St. Petersburg, FL

    727 502-8129 (voice)
    727 502-8182 (FAX)
    Hours_of_Service: M-F, 8:00-4:00 ET

Why was the data set created?

The purpose of this project was to collect data suitable for deriving the depth calibration function and coefficients of EAARL-B data. To ensure that St. Petersburg Coastal and Marine Science Center (SPCMSC) data management protocols were followed, this survey was assigned a USGS field activity number (FAN), 2014-304-FA. Additional survey and data details are available at http://cmgds.marine.usgs.gov/fan_info.php?fan=2014-304-FA

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: 19-Mar-2015 (process 1 of 4)
    The data were collected using a Cessna 310 aircraft. The EAARL-B laser scanner collects the data using a green-wavelength (532-nanometer) raster scanning laser, while a digital camera acquires a visual record of the flight. The data are stored on hard drives and archived at the USGS office in St. Petersburg, Florida. The navigational data were processed and then, along with the raw data, were downloaded into ALPS (20140715). Data were converted from units of time to x,y,z points for elevation, which were then filtered, manually edited and quality checked to ensure anomalies and noise were addressed to specification. The input parameters for the RCF were: grid cell size (buffer) = 1000 cm x 1000 cm; vertical tolerance (vertical width) = 100 cm; minimum number of points for consensus = 3; overlap factor = 4. Person who carried out this activity:
    Christine Kranenburg
    Cherokee Nation Technology, U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center, St. Petersburg, FL
    Computer Scientist
    600 4th Street South
    St. Petersburg, FL

    727 502-8129 (voice)
    Hours_of_Service: M-F, 8:00-4:00 ET
    Date: 23-Feb-2016 (process 2 of 4)
    ALPS exported the WGS84 submerged topography from .pbd format to a LAS file. LAStools was used to compress the LAS file into a LAZ file. Person who carried out this activity:
    Christine Kranenburg
    Cherokee Nation Technology, U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center, St. Petersburg, FL
    Computer Scientist
    600 4th Street South
    St. Petersburg, FL

    727 502-8129 (voice)
    Hours_of_Service: M-F, 8:00-4:00 ET
    Date: 04-Jan-2017 (process 3 of 4)
    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)
    Date: 13-Oct-2020 (process 4 of 4)
    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)
  3. What similar or related data should the user be aware of?
    Nayegandhi, A., Brock, J.C., and Wright, C.W., 2009, Small footprint, waveform-resolving lidar estimation of submerged and subcanopy topography in coastal environments: International Journal of Remote Sensing v. 30 no. 4, p. 861-878.

    Online Links:

    Wright, C.W., Kranenburg, C.J., Troche, R.J., Mitchell, R.W., and, Nagle, D.B.,, 2016, Depth calibration of the experimental advanced airborne research lidar, EAARL-B: U.S. Geological Survey Open-File Report 2016–1048.

    Online Links:

    Wright, C.W., Kranenburg, C., Battista, T.A., and Parrish, C., 2016, Depth calibration and validation of the Experimental Advanced Airborne Research Lidar, EAARL-B: Journal of Coastal Research Special Issue, No. 76, pp. 4–17.

    Online Links:

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

  1. How well have the observations been checked?
    The expected accuracy of the measured variables is as follows: attitude within 0.05 degree; 3 centimeters nominal ranging accuracy. Vertical accuracy of bathymetric data is depth-dependent and is assessed relative to International Hydrographic Organization Standards defined in International Hydrographic Bureau, 2008, IHO Standards for Hydrographic Surveys (5th ed.): International Hydrographic Organization Special Publication No. 44, 36 p. [Available at http://www.iho.int/iho_pubs/standard/S-44_5E.pdf.]. Quality checks are built into the data-processing software.
  2. How accurate are the geographic locations?
    Raw elevation measurements have been determined to be within 1 meter in horizontal accuracy.
  3. How accurate are the heights or depths?
    As expected, the Total Vertical Uncertainty (TVU) of this uncalibrated data does not meet the IHO minimum standards for hydrographic surveys for depths greater than 10 m. Refer to USGS Open-File Report 2016-1048 for a detailed explanation of the methods used to assess vertical accuracy. Vertical accuracies may vary based on the type of terrain, satellite configuration and the accuracy of the GPS and aircraft-attitude measurements.
  4. Where are the gaps in the data? What is missing?
    These point-cloud data may appear sparse or nonexistent, which is a result of automated filtering, removal by manual editing or lack of survey coverage.
  5. How consistent are the relationships among the observations, including topology?
    The data coverage area specified for this project was processed without known issues.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?
Access_Constraints: None
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
    Attn: Christine Kranenburg
    Computer Scientist
    600 4th Street South
    St. Petersburg, FL

    727 502-8129 (voice)
    Hours_of_Service: M-F, 8:00-4:00 ET
  2. What's the catalog number I need to order this data set? FLA2014_EAARLB_FLL_Uncalibrated_ST_z17_wgs84_mosaic.laz
  3. What legal disclaimers am I supposed to read?
    Although these data have been processed successfully on a computer system at the U.S. Geological Survey (USGS), no warranty expressed or implied is made regarding the display or utility of the data on any other system, or for None 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?
  5. Is there some other way to get the data?
    Contact U.S. Geological Survey for details.

Who wrote the metadata?

Last modified: 13-Oct-2020
Metadata author:
Christine Kranenburg
Cherokee Nation Technology Solutions, U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center, St. Petersburg, FL
Computer Scientist
600 4th Street South
St. Petersburg, FL

727 502-8129 (voice)
Hours_of_Service: M-F, 8:00-4:00 ET
Metadata standard:
Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)

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