Data Management Plan

This lidar point data set was collected during low tide conditions along an approximately 500-700 meter wide strip of the Southern

California coastline within an area extending south from Long Beach to the US/Mexico border. Data were collected in Los Angeles, Orange

and San Diego counties from south of the Downtown Long Beach Marina in Long Beach, California to north of Encinitas City on November 24, 2007

between 20:59 and 24:00 UTC. Data were collected in San Diego County from north of Oceanside to south of the United States-Mexico border

near Playas de Tijuana, Baja California, Mexico on November 23, 2007 between 21:19 and 23:32 UTC. Data set features include water, beach,

cliffs, and top of cliffs. The all points data set contains the complete point cloud of first and last return elevation and laser intensity

measurements recorded during the fall 2007 airborne lidar survey conducted semi-annually by the University of Texas at Austin for the

Southern California Beach Processes Study.

The data set was generated by the processing of laser range, scan angle, and aircraft attitude data collected using an Optech Inc.

Airborne Laser Terrain Mapper (ALTM) 1225 system and geodetic quality Global Positioning System (GPS) airborne and ground-based receivers.

Instrument settings and parameters during survey were:

Nominal on-ground beam diameter: 25 cm

Pulse rate: 25 kHz

Maximum number of returns recorded: 2

Minimum separation between detected returns from a single pulse: 4.3 m

Laser wavelength: 1064 nm

Frequency of GPS sampling: 1 Hz

Frequency of IMU sampling: 50 Hz; Scan angle: +/- 20 degrees

Nominal height of instrument above ground: 1100 m

Nominal single-swath pulse density: 2 m

Nominal aggregate pulse density: 0.75

Nature of vertical control: Kinematic and static GPS points

Original contact information:

Contact Name: Roberto Gutierrez

Contact Org: University of Texas at Austin Center for Space Research

Title: Research Associate in Geodesy and Geophysics

Phone: 512.471.5573

Email: oskar@mail.utexas.edu

Process Steps:

• ALTM range files were downloaded from the Optech ALTM 1225 system and decoded using Optech's REALM 3.0 tape decode program.
• Raw GPS data were downloaded from three Ashtech Z-12 GPS receivers. One receiver collected in-flight aircraft data; the other two collected data during flight time at separate base stations. The GPS data were converted into RINEX2 format with pseudorange smoothing applied. 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 ephemerides from the International GPS Service (IGS) with respect to selected CORS sites. 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 ephemerides. Coordinates for base stations and trajectories were in the International Terrestrial Reference Frame of 2000 (ITRF00). Aircraft trajectories were transformed from the ITRF00 to North American Datum of 1983 (NAD83) using the Horizontal Time Dependent Positioning (HDTP) software (Snay, 1999).
• The 1 Hz GPS trajectory and 50 Hz aircraft inertial measurement unit (IMU) data were combined in Applanix's POSProc version 4.2 to compute an aided inertial navigation solution (INS) and a 50 Hz, smoothed best estimate of trajectory (SBET). The POSPac software employs a Kalman filter to obtain a blended navigation solution. Afterwards, smoothing was applied to the solution to obtain the SBET for the aircraft.
• The SBET, laser range observations, scanner position information, and GPS/internal clock files were processed in the Realm 2.27 software suite to generate uncalibrated lidar data points in the Universal Transverse Mercator (UTM) projection. Lidar point data were compared to 1998 ATM LIDAR data over several cross-track piers and roads 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 DEMs were inspected for horizontal or vertical anomalies. Data collected on November 24, 2007, were compared to kinematic GPS points collected along the E. Pacific Coast Hwy near Laguna Beach. Data collected on November 23, 2007, were compared to kinematic GPS points collected in a parking lot near North Torrey Pines Road. After system calibration and initial quality control step, the adjusted lidar x,y,z-point data were generated by REALM software and output using the UTM Zone 11 coordinate system with elevations being heights above the GRS-80 reference ellipsoid (HAE). The output format from REALM 2.27 is a headerless space-delimited 9-column ASCII file that contains: Column 1 = the point time tag in seconds in the GPS week; Columns 2-4 = the UTM Zone 11 North easting, UTM Zone 11 North northing and height above ellipsoid (HAE) of the first lidar return; Columns 5-7 = the UTM Zone 11 North easting, UTM Zone 11 North northing and HAE of the last lidar return; and Columns 8 & 9 = the laser backscatter intensity of the first and last returns.
• Heights above the GRS80 ellipsoid (HAE) were converted to orthometric heights with respect to the North American Vertical Datum of 1988 (NAVD88), using the GEOID99 model. GPS time tags were used to separate the data collected on a single day into distinct passes. The resulting pass data sets were then parsed into 3.75-minute USGS quarter-quadrangle components containing the complete point cloud. Each output file includes data points found within a 20 meter buffer area surrounding each quarter quadrangle. Outlier data points that exceeded designated elevation thresholds (< -20 m or > 250 m) were eliminated during the parsing process.
• 2011-03-01 00:00:00 - The NOAA Office for Coastal Management (OCM) received the lidar files in ASCII format. The files contained lidar intensity and elevation measurements. OCM performed the following processing for data storage and Digital Coast provisioning purposes: 1. Data converted from UTM coordinates to geographic coordinates. 2. Data converted from NAVD88 heights to ellipsoid heights using GEOID99. 3. Data converted from dual return xyz format to xyz text format with return numbers to las format. 4. The LAS data were sorted by latitude and the headers were updated.

This data can be obtained on-line at the following URL: https://coast.noaa.gov/dataviewer

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