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2002 NASA/USGS Airborne LiDAR Assessment of Coastal Erosion (ALACE) Project for California, Oregon, and Washington Coastlines

Laser beach mapping uses a pulsed laser ranging system mounted onboard an aircraft to measure ground elevation and coastal topography. The laser emits laser beams at high frequency and is directed downward at the earth's surface through a port 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 aircraft 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.

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    Distribution Formats
    • LAZ
    Distributor Distributor information not available
    Point of Contact
    Documentation links not available.
    • DOI/USGS > United States Geological Survey, U.S. Department of the Interior
    • National Aeronautics and Space Administration (NASA)
      • publication: unknown
      Data Presentation Form: Digital image
      Dataset Progress Status Complete
      Data Update Frequency: Not planned
      Supplemental Information: This data set was collected with the NASA Airborne Topographic Lidar 3 (ATM3) LIDAR (LIght Detection and Ranging) instrument which was designed and developed by the NASA Observational Science Branch (OSB Code 972) Goddard Space Flight Center, Wallops Island VA. The ATM3 measures the time of flight of a narrow pulse (5 nanoseconds) of green laser light (532 nm) from the aircraft to the ground and back to the aircraft. The laser is pulsed at 5000 Hz and the pulses are reflected from a 22 degree off-nadir scanning mirror rotating at 20 Hz which directs the laser light and the telescope view in an elliptical scan pattern under the aircraft. The telescope collects the reflected laser light which passes through a narrow bandpass filter (to reject background light) and is detected by a photomultiplier tube detector. The ATM3 time of flight measurements are calibrated and combined with GPS data (to provide position) and aircraft inertial gyro data (to provide the aircraft attitude when each laser measurement was recorded) resulting in a calculated latitude, longitude, and elevation for each laser spot in the 250 laser shot elliptical scan under the aircraft. The scan pattern (at 22 degrees off nadir) covers a width of ~ 560 meters from a nominal aircraft altitude of 700 meters. Depending on aircraft ground speed, several consecutive scans may overlap along the aircraft flight track. Normally parallel flight tracks will be flown with ~20% overlap to cover areas wider than a single ATM3 scan width. The resultant data set is normally resampled and binned to create a digital elevation model of the desired area. Note: The Spatial Reference section of this document may lack fully FGDC-compliant information regarding projection parameters (i.e., Central meridian, false Northing, etc.). The State Plane or UTM Zone will be supplied, and the corresponding parameters can be found in Appendix C of: Snyder, John, 1987, Map Projections, a Working Manual (U.S. Geological Survey Professional Paper 1395): Washington, U.S. Government Printing Office.
      Purpose: This data was collected as part of an effort by the USGS and NASA to map beach topography and assess beach change for the states of California, Oregon and Washington.
      Time Period: 2002-09-18  to  2002-10-03
      Spatial Reference System:
      Spatial Bounding Box Coordinates:
      N: 48.389465
      S: 36.933602
      E: -119.611
      W: -128.111
      Spatial Coverage Map:
      • Bathymetry/Topography
      • lidar
      • laser
      • beach
      • digital elevation model
      • DEM
      • erosion
      • United States
      • California
      • Oregon
      • Washington
      Use Constraints No constraint information available
      Fees Fee information not available.
      Lineage Statement Lineage statement not available.
      • DOC/NOAA/NESDIS/NGDC > National Geophysical Data Center, NESDIS, NOAA, U.S. Department of Commerce
      Processing Steps
      • The xyz coordinates of this data set were transformed from ITRF_2000 to ITRF_1994 using datum transformation parameters from the National Geodetic Surveys HTDP software.
      • The vertical values in this data set have been filtered through visual inspection to find abnormally high and abnormally low values. In addition, these data have been filtered using a spatial filtering program that identifies and discards outlier elevation measurements. This program reads each elevation measurement within a file and identifies "spatially close" points (i.e. those neighboring points within a fixed radius of the point). The mean and standard deviation is calculated using the elevations of these points. If the elevation difference from the mean of the point under consideration is more than 2 standard deviations and greater than a defined distance the point is discarded.
      • The NOAA National Geophysical Data Center (NGDC) received lidar data files via ftp transfer from the NOAA Coastal Services Center. The data are currently being served via NOAA CSC Digital Coast at The data can be used to re-populate the system. The data are archived in LAS or LAZ format. The LAS format is an industry standard for LiDAR data developed by the American Society of Photogrammetry and Remote Sensing (ASPRS); LAZ is a loseless compressed version of LAS developed by Martin Isenburg ( The data are exclusively in geographic coordinates (either NAD83 or ITRF94). The data are referenced vertically to the ellipsoid (either GRS80 or ITRF94), allowing for the ability to apply the most up to date geoid model when transforming to orthometric heights.

      Metadata Last Modified: 2013-05-07

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