May 2002 Lidar Point Data of Southern California Coastline: Dana Point to Point La Jolla

This data set contains lidar point data from a strip of Southern California coastline

(including water, beach, cliffs, and top of cliffs) from Dana Point to Point La Jolla. 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 is installed in

a single engine Cessna 206 (tail number N4589U) owned and operated by the Texas State Aircraft Pooling Board.

The lidar data set described by this document was collected at low tide on 22 May 2002 (14202) between 18:20 and 21:39 UTC

(actual data collection). Conditions on that day were light clouds along the shoreline as well as offshore. 99d118 instrument

settings for this flight were; laser pulse rate: 25kHz, scanner rate: 26Hz (28Hz for calibration target), scan angle:

+/-20deg, beam divergence: narrow, altitude: 680-780m AGL for first half of flight and 900-950 for second half of flight,

and ground speed: 83-125kts. Two GPS base stations (Scripps pier and San Onofre Power Plant) were operating during the survey.

The survey included 3 shoreline passes between Dana Point and Point La Jolla as well as one offshore pass along the 20m

isobath. 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.

Original contact information:

Contact Name: Julie Thomas/Randy Bucciarelli

Contact Org: SCBPS/CDIP, Scripps Institution of Oceanography

Title: Project Managers

Phone: 858-534-3032

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.

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quad names: Dana Point, San Clemente, San Onofre Bluff, Las Pulgas Canyon, Oceanside, San Luis Rey, Encinitas, Del Mar,

La Jolla

The ALTM 1225 has the following specifications: operating altitude = 410-2,000 m AGL; 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 = 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.

None planned, as needed

This data was collected in partnership with Scripps Institution of Oceanography,

The University of California, San Diego. Any conclusions drawn from analysis of this information are not the responsibility

of the Bureau of Economic Geology or the University of Texas at Austin, NOAA, the OCM or its partners.

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

;

none

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.

Selected portions from each lidar data set (last return only) were used to generate

a 1m x 1m digital elevation model (DEM). Data estimated to have a horizontal accuracy of 0.01-0.03m from ground surveys

using kinematic GPS techniques were superimposed on the lidar DEM and examined for any mismatch between the horizontal

position of the ground GPS and the corresponding feature on the lidar DEM. Horizontal agreement between the ground kinematic

GPS and the lidar was within the resolution of the 1m x 1m DEM.

Ground GPS surveys were conducted within the lidar survey area to acquire ground

"truth" information. The ground survey points are estimated to have a vertical accuracy of 0.01-to-0.03m. The parking lot

at Torrey Pines State Park and the Scripps Pier were surveyed using kinematic GPS techniques. A lidar data set was sorted

to find data points that fell within 0.5m of a ground GPS survey point. The mean elevation difference between the lidar

and the ground GPS was used to estimate and remove an elevation bias from the lidar. The standard deviation of these

elevation differences provides estimates of the lidar precision. The May 2002 lidar data set was determined to have an

elevation bias of 0.19m when compared to ground truth. The 0.19m bias was removed so that mean lidar elevations conform

to NAVD88 with an RMSE of 0.10m.

Data were edited by an automated method to remove obvious outliers above a threshold of 150m.

Not Applicable