EAARL Coastal Topography-Northern Gulf of Mexico

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Frequently anticipated questions:


What does this data set describe?

Title: EAARL Coastal Topography-Northern Gulf of Mexico
Abstract:
ASCII xyz point cloud data were produced from remotely-sensed, geographically-referenced elevation measurements in cooperation with the U.S. Geological Survey (USGS) and National Air and Space Administration (NASA). Elevation measurements were collected over the area using the NASA Experimental Advanced Airborne Research Lidar (EAARL), 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 beam and the reception of the reflected laser signal in the aircraft. The plane travels over the target area at approximately 50 meters per second at an elevation of approximately 300 meters. The EAARL, developed by NASA at Wallops Flight Facility in Virginia, measures ground elevation with a vertical resolution of 15 centimeters. A sampling rate of 3 kHz or higher results in an extremely dense spatial elevation data set. Over 100 kilometers of coastline can be easily surveyed within a 3 to 4 hour mission time period. When subsequent elevation maps for an area are analyzed, they provide a useful tool to make management decisions regarding land development.
For more information on Lidar science and the Experimental Advanced Airborne Research Lidar (EAARL) system and surveys, see http://ngom.usgs.gov/dsp/overview/index.php and http://ngom.usgs.gov/dsp/tech/eaarl/index.php .
Supplemental_Information:
Raw lidar data is not in a format that is generally usable by resource managers and scientists. Converting dense Lidar elevation data into a readily usable format without loss of essential information requires specialized processing. The U. S. Geological Survey's Coastal and Marine Geology (CMG) Program 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 Advanced Lidar Processing System (ALPS), a multi-tiered processing system developed by a USGS/NASA collaborative project. Specialized processing algorithms are used to convert raw waveform Lidar data acquired by the EAARL to georeferenced spot (x,y,z) returns for "first surface" and "bare earth" topography. These data are then converted to the North American Datum of 1983 and the North American Vertical Datum of 1988 (using the Geoid 03 model). The files are in the Quarter Quad tiling format and the exact tile location is contained in the filename at n88_########_mf_be where ####### is the Quarter Quad tile ID.The development of custom software for creating these data products has been supported by the USGS CMG Program's 'Decision Support for Coastal Parks, Sanctuaries, and Preserves' project. Processed data products are used by the USGS CMG Program's 'National Assessments of Coastal Change Hazards Project' to quantify the vulnerability of shorelines to coastal change hazards such as severe storms, sea-level rise, and shoreline erosion and retreat.
  1. How might this data set be cited?
    U. S. Geological Survey, 20081027, EAARL Coastal Topography-Northern Gulf of Mexico: Data Series 384, U. S. Geological Survey, FISC Saint Petersburg.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -88.875
    East_Bounding_Coordinate: -84.5
    North_Bounding_Coordinate: 30.625
    South_Bounding_Coordinate: 29.375
  3. What does it look like?
    http://pubs.usgs.gov/ds/384/html/images/GUIS_west_txt.gif (GIF)
    EAARL Coastal Topography-Northern Gulf of Mexico - West
    http://pubs.usgs.gov/ds/384/html/images/NGOM_FL_east.gif (GIF)
    EAARL Coastal Topography-Northern Gulf of Mexico - East
  4. Does the data set describe conditions during a particular time period?
    Calendar_Date: 19-Sep-2004
    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?
      This is a Raster data set. It contains the following raster data types:
      • Dimensions 106 x 173 x 1, 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: 0.000000
      False_Easting: 500000.000000
      False_Northing: 0.000000
      Planar coordinates are encoded using row and column
      Abscissae (x-coordinates) are specified to the nearest 2.000000
      Ordinates (y-coordinates) are specified to the nearest 2.000000
      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 1/298.257222.
      Vertical_Coordinate_System_Definition:
      Altitude_System_Definition:
      Altitude_Datum_Name: North American Vertical Datum of 1988
      Altitude_Resolution: 0.15 m
      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:
    This Digital Elevation Model is a GeoTIFF. It is raster data consisting of cells. Each cell has an elevation value associated with it.
    Entity_and_Attribute_Detail_Citation:
    The variables measured by EAARL are: distance between aircraft and GPS satellites (m), attitude information (roll, pitch, heading in degrees), scan angle (degrees), second of the epoch (sec), and 1ns time-resolved return intensity waveform (digital counts). Z value is referenced to orthometric elevations derived from National Geodetic Survey Geoid Model, Geoid03.

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?
    The U. S. Geological Survey is providing these data "as is", and the U. S. Geological Survey disclaims any and all warranties, whether expressed or implied, including (without limitation) any implied warranties of merchantability or fitness for a particular purpose. In no event will the U. S. Geological Survey be liable to you or to any third party for any direct, indirect, incidental, consequential, special, or exemplary damages or lost profits resulting from any use or misuse of these data. Acknowledgement of the U.S. Geological Survey, Florida Integrated Science Center as a data source would be appreciated in products developed from these data, and such acknowledgement as is standad for citation and legal practices for data source is expected by users of this data. Sharing 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 data sets for the same area from other time periods may be inaccurate due to inconsistencies resulting from changes in photo interpretation, 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?
    Jacobs Technology, contracted to USGS
    Attn: Amar Nayegandhi or John Brock at USGS
    Computer Scientist
    600 4th Street South
    Saint Petersburg, FL
    USA

    727-803-8747 (voice)
    anayegandhi@usgs.gov
    Hours_of_Service: M-F 8:30-5:00 EST

Why was the data set created?

The ASCII elevation data can be used to create raster Digital Elevation Models (DEMs). The purpose of this project is to produce highly detailed and accurate digital elevation maps of the post Hurricane Ivan data for use as a management tool and to make this data available to natural resource managers and research scientists.

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: 01-Dec-2007 (process 1 of 3)
    The data are collected using a Cessna 310 aircraft. The NASA Experimental Advanced Airborne Research Lidar (EAARL) laser scanner collects the data using a green (532nm) 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 U. S. Geological Survey, FISC St. Petersburg office and the NASA office at Wallops Flight Facility. The navigational data are processed at Wallops Flight Facility. The navigational and raw data are then downloaded into the Advanced Lidar Processing System (ALPS). Data are converted from units of time to x,y,z points for elevation. The derived surface data can then be converted into raster data (geotiffs). Person who carried out this activity:
    Jacobs Technology, U. S. Geological Survey, FISC St. Petersburg
    Attn: Amar Nayegandhi
    Computer Scientist
    600 4th Street South
    Saint Petersburg, FL
    USA

    727-803-8747 (voice)
    anayegandhi@usgs.gov
    Hours_of_Service: M-F, 8:00-5:00 EST
    Date: 10-Mar-2008 (process 2 of 3)
    Metadata imported into ArcCatalog from XML file. Person who carried out this activity:
    U. S. Geological Survey
    Attn: Metadata Specialist
    Metadata Specialist
    600 4th Street South
    Saint Petersburg, FL
    USA

    727-803-8747 (voice)
    Date: 24-Jan-2017 (process 3 of 3)
    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
  3. What similar or related data should the user be aware of?
    Nayegandhi, A., Brock, J.C., Wright, C.W, 2008, Small footprint, waveform-resolving lidar estimation of submerged and subcanopy topography in coastal environments: International Journal of Remote Sensing 30(4), pp. 861-878.

    Brock, J.C., C.W. Wright, A.H. Sallenger, W.B. Krabill, and R.N. Swift, 2002, Basis and methods of NASA Airborne Topographic Mapper lidar surveys for coastal studies: Journal of Coastal Research 18(1), pp. 1-13.

    Sallenger, A.H., C.W. Wright, and J. Lillycrop, 2005, Coastal impacts of the 2004 hurricanes measured with airborne lidar; initial results: Shore and Beach 73(2&3), pp. 10-14.


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 are as follows: attitude within 0.07 degree, 3 cm nominal laser ranging accuracy, and vertical elevation accuracy of +/-15 cm for the topographic surface. 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 horizontal accuracy.
  3. How accurate are the heights or depths?
    Elevations of the DEM are vertically consistent with the point elevation data, +/-15 cm.
  4. Where are the gaps in the data? What is missing?
    Several regions of the dataset are labeled as "No Data", which corresponds to a cell value of -32767 m in the GeoTIFF file. These "No Data" areas are a result of the survey not covering a particular region, optical water depth of greater than 1.5 Secchi disc depths, or the manual removal of lidar processing artifacts.
  5. How consistent are the relationships among the observations, including topology?
    The files are in the Quarter Quad tiling format and the exact tile location is contained in the filename at n88_########_mf_be where ####### is the Quarter Quad tile ID.See QQ_naming_convention.doc in the 'extras' directory.

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 and National Aeronautics and Space Administration request to be acknowledged as originators of the data in future products or derivative research.
  1. Who distributes the data set? (Distributor 1 of 1)
    U. S. Geological Survey
    Attn: Project Manager
    Project Manager
    600 4th Street South
    Saint Petersburg, FL
    USA

    727 803-8747 (voice)
    Hours_of_Service: M-F 8:30-5:00 EST
  2. What's the catalog number I need to order this data set? DS_384
  3. What legal disclaimers am I supposed to read?
    The U. S. Geological Survey shall not be held liable for improper or incorrect use of the data described and/or contained herein. These data and related graphics are not legal documents and are not intended to be used as such. The information contained in these data is dynamic and may change over time. The data are not better than the original sources from which they were derived. It is the responsibility of the data user to use the data appropriately and consistent within the limitations of geospatial data in general and these data in particular. The related graphics are intended to aid the data user in acquiring relevant data; it is not appropriate to use the related graphics as data. The U. S. Geological Survey gives no warranty, expressed or implied, as to the accuracy, reliability, or completeness of these data. It is strongly recommended that these data are directly acquired from a U. S. Geological Survey server and not indirectly through other sources which may have changed the data in some way. Although these data have been processed successfully on a computer system at the U. S. Geological Survey, no warranty expressed or implied is made regarding the utility of the data on another system or for general or scientific purposes, nor shall the act of distribution constitute any such warranty. This disclaimer applies both to individual use of the data and aggregate use with other data.
  4. How can I download or order the data?
    • Availability in digital form:
      Data format: TIFF (version 2) GeoTIFF
      Network links: http://pubs.usgs.gov/ds/384/data_files/fs/
      Media you can order: DVD (format DVD)
    • Cost to order the data: vary

    • Special instructions:
      contact USGS
    • How long will it take to get the data?
      vary
  5. Is there some other way to get the data?
    Call USGS for Details

Who wrote the metadata?

Dates:
Last modified: 17-Apr-2018
Metadata author:
U. S. Geological Survey
Attn: Metadata Specialist
Metadata Specialist
600 4th Street South
Saint Petersburg, FL
USA

727-803-8747 (voice)
Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)

This page is <https://cmgds.marine.usgs.gov/catalog/spcmsc/ds-384metadata.faq.html>
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