ASIS_LiDAR

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Frequently-anticipated questions:

What does this data set describe?

Title: ASIS_LiDAR
Abstract:
Elevation maps (also known as Digital Elevation Models or DEMs) of Assateague Island National Seashore were produced from remotely-sensed, geographically-referenced elevation measurements in cooperation with the National Aeronautics and Space Administration (NASA) and the National Park Service (NPS). Point data in ASCII text files were interpolated in a GIS to create a grid or digital elevation model of each beach surface.Elevation measurements were collected in Maryland and Virginia, over Assateague Island National Seashore using the NASA Experimental Advanced Airborne Research LiDAR (EAARL), a pulsed laser ranging system mounted onboard an aircraft to measure ground elevation 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 beach at approximately 60 meters per second while surveying from the low-water line to the landward base of the sand dunes. The EAARL, developed by NASA located 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. The ability to sample large areas rapidly and accurately is especially useful in morphologically dynamic areas such as barrier beaches. Quick assessment of topographic change can be made following storms comparing measurements against baseline data. When subsequent elevation maps for an area are analyzed, they provide a useful tool to make management decisions regarding coastal development.
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 Park Service GIS specialists, managers, and scientists. The primary tool used in the conversion process is Airborne LiDAR Processing System (ALPS), a multitiered processing system developed by a USGS/NASA collaborative for the use of topographic LiDAR in coastal change assessment. 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 NAD83 horizontal and NAVD88 vertical datum (using the Geoid 99 model). The final products are 2x2-km map tiles written out in a standard GEOtiff format with associated metadata information. These tiles are created for visual interpretation and regional quantitative analysis. Metadata files include the standard FGDC format.
  1. How should this data set be cited?

    United States Geological Survey, FISC St. Petersburg 2007, Open File Report 2007-1176

    Online Links:

    • none

    Other_Citation_Details:
    The United States Geological Survey (USGS), in cooperation with the National Park Service (NPS) and the National Aeronautics and Space Administration (NASA), is to provide the coastal management community with usable, useful digital elevation products. The USGS processes aircraft LiDAR data (provided by NASA), develops software tools and algorithms to use and analyze the data and make products available to the coastal management community through a variety of media, including the internet, CD-ROMs, DVDs and data reports.

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -75.386493
    East_Bounding_Coordinate: -75.363670
    North_Bounding_Coordinate: 37.856897
    South_Bounding_Coordinate: 37.838799

  3. What does it look like?



  4. Does the data set describe conditions during a particular time period?

    Calendar_Date: 27-Aug-2004
    Currentness_Reference: ground condition

  5. What is the general form of this data set?

    Geospatial_Data_Presentation_Form: raster digital data

  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 2000 x 2000 x 1, type Grid Cell

    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
      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 attributes measured are as follows: variables measured by EAARL - distance between aircraft and GPS satellites (m), attitude information (roll, pitch, heading in degrees), scan angle (degrees), second of the epoch (sec), 1-ns time-resolved return intensity waveform (digital counts), and co-registered digital aerial photography. For derived variables, WGS84, NAD83 or other UTM eastings and northings (m), NAVD88 elevations (m), and peak amplitude (intensity). For derived surfaces, bare-earth elevations, and first-return elevations.

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)

  2. Who also contributed to the data set?

    The US Geological Survey, FISC St. Petersburg, would like to acknowledge NASA Goddard Space Flight Center for their cooperation and assistance in the development of the data. The USGS would also like to acknowledge National Park Service management and personnel at Assateague Island National Seashore.

  3. To whom should users address questions about the data?

    United States Geological Survey, FISC St. Petersburg
    c/o Dr. John C. Brock
    Physical Oceanographer
    600 4th Street South
    St. Petersburg, Florida 33701-
    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?

One goal of the Project is to produce highly detailed and accurate digital elevation maps (DEMs) of National Seashores and coastal parks for use as a management tool and to make these maps available to natural resource managers within the parks.

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: 2004 (process 1 of 1)
    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, FISC St. Petersburg office and the NASA Wallops office. The navigational data are processed at Wallops. 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:

    United States Geological Survey
    c/o Amar Nayegandhi
    Computer Scientist
    600 4th Street South
    St. Petersburg, Florida 33701-
    USA

    727-803-8747 (voice)

    Hours_of_Service: 8:00am to 5:00pm Monday thru Friday, EST
    Contact_Instructions: Call Survey for Details
  3. What similar or related data should the user be aware of?

    Brock, J.C.; Wright, C.W.; Sallenger, A.H; K, 2003, Basis and Methods of NASA Ariborne Topographic Mapper LiDAR Surveys for Coastal Studies: Journal of Coastal Research, West Palm Beach, FL.

    John Brock and Asbury Sallenger, US Geological Survey, 2001, Airborne Topographic LiDAR Mapping for Coastal Science and Resource Management: US Geological Survey, St. Petersburg, FL.

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 verticle elevation accuracy of +/- 15cm (bare earth). 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 1.5 meter horizontal accuracy. Processing steps (grid interpolation) may introduce additional error which has not been tested at the time of this publication.

  3. How accurate are the heights or depths?

    Elevations of the DEM are vertically consistent with the point elevation data, +/- 15cm.

  4. Where are the gaps in the data? What is missing?

    unknown

  5. How consistent are the relationships among the observations, including topology?

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 thes data for any given purpose. The user assumes the entire risk related to the use of these data. These data sets are not for navigational purposes. 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 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 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.

  1. Who distributes the data set? (Distributor 1 of 1)

    U.S. Geological Survey FISC St. Petersburg
    600 4th Street South
    St. Petersburg, FL 33701
    USA

    727-803-8747 (voice)

    Hours_of_Service: 8:30-5:00 M-F EST
    Contact_Instructions: Call Office for Details
  2. What's the catalog number I need to order this data set?

        Open File Report 2007-1176

  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?

  5. Is there some other way to get the data?

    Call USGS for Details

Who wrote the metadata?

Dates:
Last modified: 02-Aug-2007
Metadata author:
United States Geological Survey
600 4th Street South
St. Petersburg, Floirda 33701
USA

727-803-8747 (voice)

Hours_of_Service: 8:30-5:00 M-F EST
Contact_Instructions: Call Survey for Details
Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)
Metadata extensions used:

Generated by mp version 2.8.6 on Thu Nov 09 10:50:32 2006