April 2004 Lidar Point Data of Southern California Coastline: Dana Point to Point La Jolla

This data set contains lidar point data (Geodetic Coordinates) from a strip of Southern California

coastline (including water, beach, cliffs, and top of cliffs) from Dana Point to 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 was installed in a twin engine Partenavia P-68

(tail number N3832K) owned and operated by Aspen Helicopter, Inc. The lidar data set described by this document was collected

on 2 April 2004 between 19:14 and 21:20 UTC. Julian Day 09304 (see Lineage, Source_Information, Source_Contribution for pass

information). Conditions on 4 April were low clouds at 2500-3000 ft and lower over La Jolla. 99d118 instrument settings for

these flights were; laser pulse rate: 25kHz, scanner rate: 26Hz, scan angle: +/- 20deg, beam divergence: narrow, altitude:

300-600m AGL, and ground speed: 95-120kts. Two GPS base stations were operating during each day of the survey, Point Loma

and San Onofre on 08306 and Seal Beach and San Onofre on 08406 (see Lineage, Source_Information, Source_Contribution for

coordinates). 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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quarter quad names: Del Mar, Dana Point, Encinitas, La Jolla, Las Pulgas Canyon, Oceanside, San Clemente, San Luis Rey,

San Onofre Bluff

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.

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

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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 was 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 April 2004 lidar data set was determined to have an elevation bias of 0.153 m in TIM1

and 0.11 m in TIM2 when compared to ground truth. The bias was removed so that mean lidar elevations have a standard deviation

of 0.053 m and a vertical accuracy (1.96*RMSE) of 0.104 m.

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

Not Applicable