EAARL Bare Earth Topography-Fire Island National Seashore

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Frequently anticipated questions:


What does this data set describe?

Title: EAARL Bare Earth Topography-Fire Island National Seashore
Abstract:
A bare earth elevation map (also known as a Digital Elevation Model or DEM) of Fire Island National Seashore was produced from remotely-sensed, geographically-referenced elevation measurements in cooperation with the U.S. Geological Survey (USGS), National Air and Space Administration (NASA), and the National Park Service (NPS). 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 m. 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 Park Service 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 converts raw lidar data into a GIS-compatible map product to be provided to National Park Service 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 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 "bald 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). Each file contains data located in a 2 km by 2 km tile where the upper left bound can be quickly assessed through the file name. The first number in the filename (e######) is the left most UTM easting coordinate in meters, the second number (n#######) is the top most UTM northing coordinate in meters, and the third number (##) is the UTM zone the tile is located.
  1. How might this data set be cited?
    U.S. Geological Survey, 2006, EAARL Bare Earth Topography-Fire Island National Seashore: Open File Report 1384.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -73.237872
    East_Bounding_Coordinate: -72.760761
    North_Bounding_Coordinate: 40.783611
    South_Bounding_Coordinate: 40.627676
  3. What does it look like?
    http://pubs.usgs.gov/of/2006/1384/images/fiis_be.gif (GIF)
    EAARL Bare Earth Topography—Fire Island National Seashore
  4. Does the data set describe conditions during a particular time period?
    Calendar_Date: 25-Apr-2005
    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: Tiling Index
      This is a Raster data set. It contains the following raster data types:
      • Dimensions 2001 x 2001 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: 18
      Transverse_Mercator:
      Scale_Factor_at_Central_Meridian: 0.999600
      Longitude_of_Central_Meridian: -75.000000
      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 1.000000
      Ordinates (y-coordinates) are specified to the nearest 1.000000
      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: 15 cm
      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:
    Each pixel of the encoded GeoTIFF has an explicit elevation value associated with it. The GeoTIFF grid is encoded with a 1-meter resolution.
    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 1-ns 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?
    USGS is providing these data "as is", and USGS 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 USGS 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 Center for Coastal and Watershed Studies as a data source would be appreciated in products developed from these data, and such acknowledgement as is standard 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 USGS 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?
    Dr. John C Brock
    United States Geological Survey, Center for Coastal and Watershed Studies
    Physical Oceanographer
    600 4th Street South
    Saint Petersburg, FL
    USA

    727 803-8747 ext3088 (voice)
    727 803-2031 (FAX)
    jbrock@usgs.gov
    Hours_of_Service: Monday-Friday, 8-5, EST

Why was the data set created?

The purpose of this project was to produce a highly detailed and accurate bare earth digital elevation map of Fire Island National Seashore for use as a management tool and to make this map available to natural resource managers.

How was the data set created?

  1. From what previous works were the data drawn?
    none (source 1 of 1)
    U.S. Geological Survey, 2006, EAARL Bare Earth Topography-Fire Island National Seashore: U.S. Geological Survey Open File Report 1384, U.S. Geological Survey, Saint Petersburg, FL.

    Type_of_Source_Media: Point elevation measurements collected by the EAARL sensor.
    Source_Contribution: none
  2. How were the data generated, processed, and modified?
    Date: 01-Feb-2006 (process 1 of 4)
    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 USGS office in St. Petersburg 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 Airborne 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:
    Amar Nayegandhi
    ETI Professionals, Inc. Contracted with US Geological Survey
    Computer Scientist
    600 4th Street South
    St. Petersburg, Florida
    USA

    727-803-8747 (voice)
    Hours_of_Service: 8:00am to 5:00pm Monday thru Friday, EST
    Contact_Instructions: Call Survey for Details
    Date: 01-Jul-2006 (process 2 of 4)
    The raster dataset was opened in ERDAS IMAGINE for editing. An Area of Interest (AOI) polygon was drawn around regions of poor data quality. Poor data quality was determined visually by locating gaps in the data as well as artifacts of the lidar processing. Pixels within the AOI polygons were given a raster value of -100 to correspond with other areas of No Data. Person who carried out this activity:
    Judd Patterson
    National Park Service South Florida / Caribbean Network Inventory and Monitoring Program
    Research Assistant
    18001 Old Cutler Rd
    Miami, Florida
    USA

    (305) 252-0347 (voice)
    (305) 253-0463 (FAX)
    Date: 01-Jul-2006 (process 3 of 4)
    Metadata imported. Data sources used in this process:
    • C:\LIDAR\FIIS\LIDAR\bare_earth\e680_n4514\be_e680_n4514edit.tif.xml
    Date: 24-Jan-2017 (process 4 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)
    aallwardt@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?
    The expected accuracy of the measured variables are as follows: attitude within 0.07 degree, 3-cm nominal 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 -100 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?
    Each file contains data located in a 2-km by 2-km tile, where the upper-left bound can be assessed quickly through the file name. The first 3 numbers in the file name represent the left-most UTM easting coordinate (e###000) in meters, the next 4 numbers represent the top-most UTM northing coordinate (n####000) in meters, and the last 2 numbers (##) represent the UTM zone in which the tile is located (for example, ba_e123_n4567_20).

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?
Access_Constraints:
Any use of these data signifies a user's agreement to comprehension and compliance of the USGS Standard Disclaimer. Ensure all portions of metadata are read and clearly understood before using these data in order to protect both user and USGS interests. See section 6.3 Distribution Liability.
Use_Constraints:
Although the USGS is making these data sets available to others who may find the data of value, USGS does not warrant, endorse, or recommend the use of this data for any given purpose. The user assumes the entire risk related to the use of these data.
  1. Who distributes the data set? (Distributor 1 of 1)
    Jerry Butcher
    USGS: Center for Coastal and Watershed Studies
    Windows System Administrator
    600 4th Street South
    Saint Petersburg, FL
    USA

    727-803-8747 x3049 (voice)
  2. What's the catalog number I need to order this data set? Lidar DEM (Fire Island)
  3. What legal disclaimers am I supposed to read?
    The United States 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 United States 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 an USGS 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 United States 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: GeoTIFF GeoTIFF
      Network links: http://pubs.usgs.gov/of/2006/1384/data.htm
      Media you can order: DVD (format DVD)
    • Cost to order the data: Vary

    • Special instructions:
      Contact U.S. Geological Survey.
    • 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:
USGS Center for Coastal and Watershed Studies
Attn: Jeremy Bracone
Saint Petersburg, FL

(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/of2006-1384metadata.faq.html>
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