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April 2005 Lidar Point Data of Southern California Coastline: Long Beach to US/Mexican Border

This data set contains lidar point data (latitude/longitude) from a strip of Southern California coastline (including water, beach, cliffs, and top of cliffs) from Long Beach to the US/Mexico border. The data set was created by combining data collected using an Optech Inc. Airborne Laser Terrain Mapper (ALTM) 1225 in combination with geodetic quality Global Positioning System (GPS) airborne and ground-based receivers. The Bureau of Economic Geology, the University of Texas at Austin owns and operates an ALTM 1225 system (serial number 99d118). The system was installed in a twin engine Partenavia P-68 Observer (tail number N6602L) owned and operated by Aspen Helicopter, Inc. The lidar data set described by this document was collected on 4 and 8 April 2005; Julian Days 09405 and 09805 (see Lineage, Source_Information, Source_Contribution for pass information). 99d118 instrument settings for these flights were; laser pulse rate: 25kHz, scanner rate: 26Hz, scan angle: +/- 20deg, beam divergence: narrow, altitude: 900-1100m AGL, and ground speed: 100-125kts. Three GPS base stations (Seal Beach, Dana Point, and Point Loma, see Lineage, Source_Information, Source_Contribution for coordinates) operated during the survey. Data represented is all points including terrain, vegetation, and structures. This data also contains returns from the water surface. No processing has been done to remove returns from terrain, vegetation, structures or water surfaces.

Cite this dataset when used as a source.

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    Distribution Formats
    • LAZ
    Distributor DOC/NOAA/NOS/CSC > Coastal Services Center, National Ocean Service, National Oceanic and Atmospheric Administration, U.S. Department of Commerce
    Point of Contact Julie Thomas/Randy Bucciarelli
    SCBPS/CDIP, Scripps Institution of Oceanography
    858-534-3032
    Documentation links not available.
    Originator
    • Southern California Beach Processes Study (SCBPS)/Coastal Data Information Program (CDIP) part of Scripps Institution of Oceanography (SIO) in cooperation with Bureau of Economic Geology, University of Texas at Austin.
    Originator
    • DOC/NOAA/NOS/CSC > Coastal Services Center, National Ocean Service, National Oceanic and Atmospheric Administration, U.S. Department of Commerce
    Originator
    • Scripps Institute of Oceanography
    Originator
    • Center for Space Research, University of Texas at Austin
    Originator
    • Bureau of Economic Geology, University of Texas at Austin
    Publisher
    • DOC/NOAA/NOS/CSC > Coastal Services Center, National Ocean Service, National Oceanic and Atmospheric Administration, U.S. Department of Commerce
    Date(s)
    • publication: 2005-07-28
    Data Presentation Form: Digital image
    Dataset Progress Status Complete
    Data Update Frequency: As needed
    Supplemental Information: The ALTM 1225 (SN#99d118) lidar instrument has the following specifications: operating altitude = 410-2,000 m AGL; maximum laser pulse rate = 25 kHz; laser scan angle = variable from 0 to +/-20deg from nadir; scanning frequency = variable, 28 Hz at the 20deg scan angle; and beam divergence: narrow = 0.2 milliradian (half angle, 1/e). The ALTM 1225 does not digitize and record the waveform of the laser reflection, but records the range and backscatter intensity of the first and last laser reflection using a constant-fraction discriminator and two Timing Interval Meters (TIM). ALTM elevation points are computed using three sets of data: laser ranges and their associated scan angles, platform position and orientation information, and calibration data and mounting parameters (Wehr and Lohr, 1999). Global Positioning System (GPS) receivers in the aircraft and on the ground provide platform positioning. The GPS receivers record pseudo-range and phase information for post-processing. Platform orientation information comes from an Inertial Measurement Unit (IMU) containing three orthogonal accelerometers and gyroscopes. An aided-Inertial Navigation System (INS) solution for the aircraft_??s attitude is estimated from the IMU output and the GPS information. Wehr, A. and U. Lohr, 1999, Airborne laser scanning - an introduction and overview, ISPRS Journal of Photogrammetry and Remote Sensing, vol. 54, no.2-3, pp.68-82.
    Purpose: The data described in this document will be compared with previous and forthcoming data sets to determine rates of shoreline change along the Southern California coastline. The SCBPS program is designed to improve the understanding of beach sand transport by waves and currents, thus improving local and regional coastal management.
    Use Limitations
    • These data depict the elevations at the time of the survey and are only accurate for that time. Users should be aware that temporal changes may have occurred since this data set was collected and some parts of this data may no longer represent actual surface conditions. Users should not use this data for critical applications without a full awareness of its limitations. Any conclusions drawn from analysis of this information are not the responsibility of NOAA or any of its partners. These data are NOT to be used for navigational purposes.
    Time Period: 2005-04-04  to  2005-04-08
    Spatial Reference System: urn:ogc:def:crs:EPSG::4269 Ellipsoid in Meters
    Spatial Bounding Box Coordinates:
    N: 33.768786
    S: 32.562486
    E: -117.128845
    W: -118.205345
    Spatial Coverage Map:
    Themes
    • Bathymetry/Topography
    • shoreline
    • beach
    • lidar
    • laser
    • point file
    • Latitude
    • Longitude
    • intensity
    Places
    • US
    • California
    • San Diego
    • Pacific Ocean
    Use Constraints No constraint information available
    Fees Fee information not available.
    Source Datasets
    • Raw lidar data output from ALTM 1225
      • Description of Source: Source Contribution: Raw lidar data files. Raw lidar data from ALTM 1225 (all times UTC) 09405 Pass A (Oceanside to Dana Point) = 19:19-19:36 Pass B (Dana Point to Mexico) = 19:39-20:17 Pass C (Point Loma to Mexico) = 20:28-20:34 Pass D (Mexico to Dana Point) = 20:36-21:00 and 21:12-21:35 Pass E (Oceanside to La Jolla) = 21:45-21:59 Pass F (La Jolla to Oceanside) = 22:02 to 22:14 Calibration Passes = 21:02-21:11 09805 Pass G (Oceanside to Long Beach) = 21:37-22:20 Pass H (Long Beach to Dana Point) = 22:23-22:41 Pass I (Dana Point to Long Beach) = 22:45-23:06 Pass J (Long Beach to Dana Point) = 23:12-23:29 Calibration Passes = 23:34-23:47 Source Type: digital file
      • Temporal extent used:  2005-04-04  to  2005-04-08
    • Air and Ground GPS files from 27204, 27304, and 27404
      • Description of Source: Source Contribution: GPS data. Air and ground GPS files base station coordinates Easting, Northing, HAE in NAD83, Zone 11 (Latitude, Longitude): Seal Beach (SEAL) = 399189.009, 3733584.462, -27.9778 (N 33 44 15.0510, W 118 5 17.8191) Dana Point (DANA) = 434087.529, 3702982.315, 52.1756 (N 33 27 51.3542, W 117 42 33.5246) Point Loma (LOMA) = 477398.387, 3614791.668, 90.1348 (N 32 40 14.01098, W 117 14 27.79485) Source Type: digital file
      • Temporal extent used:  2005-04-04  to  2005-04-08
    Lineage Statement Lineage statement not available.
    Processor
    • Bureau of Economic Geology, University of Texas at Austin
    • DOC/NOAA/NOS/CSC > Coastal Services Center, National Ocean Service, National Oceanic and Atmospheric Administration, U.S. Department of Commerce
    • DOC/NOAA/NESDIS/NGDC > National Geophysical Data Center, NESDIS, NOAA, U.S. Department of Commerce
    Processing Steps
    • GPS and XYZ-Point Data Processing The National Geodetic Survey's PAGES-NT software was used to compute double differenced, ionospherically corrected, static GPS solutions for each GPS base station with precise ephemeredes from the International GPS Service (IGS). As part of the solution tropospheric zenith delays were estimated and L1 and L2 phase biases were fixed as integers. Aircraft trajectories were estimated with respect to all base stations using National Geodetic Survey's Kinematic and Rapid-Static Software (KARS) software. Trajectories were double-differenced, ionospherically corrected, bias-fixed GPS solutions computed with precise IGS ephemeredes. Coordinates for base stations and trajectories were in the International Terrestrial Reference Frame of 2000 (ITRF00). The aircraft trajectory were transformed from the ITRF00 to North American Datum of 1983 (NAD83) using the Horizontal Time Dependent Positioning (HDTP) software (Snay, 1999) The 1Hz GPS trajectory and 50Hz aircraft inertial measurement unit (IMU) data were combined in Applanix's POSProc version 2.1.4 to compute an aided inertial navigation solution (INS) and a 50Hz, smoothed best estimate of trajectory (SBET) for day 09405. On the second day of data collection (09805), due to an equipment problem, the IMU data was recorded with random data gaps onto the ALTM1225 hard drive. Because of these data gaps, the post-processed INS and SBET for 09805 was judged not acceptable. The 1Hz aircraft trajectory computed with KARS and the real-time, aided INS solution from POS-AV provided better results. The SBET (09405) and KARS trajectory (09805), laser range observations, scanner position information, and GPS/internal clock files were processed in Realm 2.27 software suite to generate lidar data points in the Universal Transverse Mercator (UTM) projection. Lidar point data were compared to GPS ground survey data and 1998 ATM lidar data to estimate lidar instrument calibration parameters: roll and pitch biases, scanner scale factor, and first/last return elevation biases. An iterative, least-squares methodology was used to estimate calibration parameters so as to minimize differences between lidar and ground GPS data. Samples of lidar data were used to create high-resolution digital elevation models (DEM); these DEM were inspected for horizontal or vertical anomalies. After system calibration and initial quality control step, the adjusted lidar x,y,z-point data were generated by REALM software and output in UTM, zone 11 with elevations being heights above the GRS-80 reference ellipsoid (HAE). The output format from REALM 2.27 was a 9-column ASCII file containing: the second in the GPS week, easting, northing and HAE of the first lidar return, the easting, northing and HAE of the last lidar return, and the laser backscatter intensity of the first and last returns. Each record contains 9 columns of data: time tag (seconds in the GPS week), first return Easting, first return Northing, first return NAVD88, last return Easting, last return Northing, last return NAVD88, first return intensity, and last return intensity. In some cases either the first or last return values may be missing (5 columns). Data Classification Processing The classification of the lidar point data was accomplished with algorithms developed at the Center for Space Research and implemented by C++ code running on PC computer using the LINUX operating system. The ASCII lidar files were converted into binary and concatenated into a processing database. Data were separated into ground and non-ground points using a lower envelope follower (LEF). A lower envelope detector is an electronic circuit used to recover information in an Amplitude Modulated (AM) signal and the concept was adapted to the problem of extracting the ground surface from the lidar signal by creating a computer analog: the lower envelope follower (LEF) The LEF was used to detect ground points, or seeds, which include pixels located on open ground or on the ground surface beneath vegetation penetrated by the laser, but excludes buildings and vegetation. The LEF operation does not detect some ground surface areas with low gradients, so detected ground pixels are augmented using an adaptive gradient flood fill procedure. The adaptive threshold value is determined as a function of surface roughness and topographic relief. The adaptive gradient flood fill procedure results in a ground mask which is used to parse individual lidar points into ground or non-ground files. In some instances, hand editing is required to ensure accuracy of the ground mask. This includes the addition of seed points along topographic ridges or removal of buildings not detected during previous steps. The 9-column binary dataset was pushed through the ground mask and each lidar point is classified as either ground or non-ground depending on its elevation with respect to a threshold above or below the estimated ground surface. Buildings are included as non-ground points. The final ground-only data points were parsed converted back into ASCII format. Using the GEOID99 geoid model, heights above the GRS80 ellipsoid were converted to orthometric heights with respect to the North American Vertical Datum of 1988 (NAVD88). The final step was parsing the data into quarter quadrangles.
    • The NOAA Coastal Services Center (CSC) received files in ASCII format. The files contained LiDAR intensity and elevation measurements. CSC performed the following processing on the data to make it available within the LiDAR Data Retrieval Tool (LDART) 1. Data returned to ellipsoid heights from NAVD88, using GEOID99. 2. Data converted to LAS format. 3. The LAS data were sorted by latitude and the headers were updated.
    • 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 http://www.csc.noaa.gov/digitalcoast/. 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 (http://www.laszip.org/). 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

    For questions about the information on this page, please email: mike.sutherland@noaa.gov