April 2008 Scripps Institute of Oceanography (SIO) Lidar of the Southern California Coastline: Long Beach to US/Mexico Border

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Two Ashtech Z-12 GPS receivers placed at precisely located base stations collected GPS data at 1 second intervals throughout the period

of airborne lidar data collection. Data collection commenced prior to take off and ceased subsequent to touch down. A third Ashtech Z-12 GPS

receiver collected in-flight GPS data at 1 second intervals. Data were downloaded and stored each day after flight completion. File names

included standardized references to location and date. These data were used for ALTM range file processing. See process steps for more

detailed information.

GPS base station locations by survey day:

April 12 (day 103), 2008: SANO, LOMA

April 13 (day 104), 2008: SANO, SEAL

GPS base station attributes:

ID: SANO

Name: HPGN-CA SDGPS01, 1990, Description: San Diego County Engineer Department GPS control point at San Onofre

NAD83 Coordinates and HAE: 33d 22m 31.08420s N, 117d 33m 54.54673s W, -5.17

ID: SEAL

Name: HPGN CA 12 01, Description: California High Precision GPS Network 12 01 (PID:DY9309)

NAD83 Coordinates and HAE: 33d 44m 15.03481s N, 118d 05m 17.76708s W, -27.228

ID: LOMA

Name: LOMA EAST, Description: NGS Control Point at Loma Point, LOMA EAST, 1994 (PID: AC6092)

NAD83 Coordinates and HAE: 32d 40m 13.99579s N, 117d 14m 27.74509s W, 90.892

| Type of Source Media: digital files

Range files are the source data collected by the ALTM 1225 sensor.

ALTM 1225 range files used for this survey are grouped by date, day of year, pass, pass location, and time of collection (all times UTC):

Spring 2008

April 12, 2008 (Day of Year = 103), HH:MM in UTC

===================================================

10308 Pass A (San Onofre to Point Loma (gap at La Jolla)) 16:14-16:50

10308 Pass B (Coronado (North Island NAS) to Playas de Tijuana) 16:53-17:02

10308 Pass C (Playas de Tijuana to Coronado (North Island NAS)) 17:03-17:10

10308 Pass D (Coronado (North Island NAS) to Playas de Tijuana) 17:14-17:23

10308 Pass E (Playas de Tijuana to Coronado (North Island NAS)) 17:28-17:35

10308 Pass F (Point Loma to Oceanside Harbor) 17:40-18:02

10308 Pass G (Oceanside Harbor to La Jolla) 18:05-18:23

10308 Pass H (La Jolla to San Onofre) 18:25-18:48

10308 Pass I (San Onofre to Oceanside) 18:50-19:00

April 13, 2008 (Day of Year = 104), HH:MM in UTC

===================================================

10408 Pass A (Camp Pendleton (Las Pulgas Road) to Long Beach (gap at Dana Point)) 17:16-17:50

10408 Pass B (Long Beach to Dana Point) 17:53-18:14

10408 Pass C (Dana Point to Long Beach) 18:18-18:36

10408 Pass D (Long Beach to Oceanside Harbor) 18:39-19:18

10408 Pass E (Oceanside Harbor to Dana Point) 19:20-19:34

10408 Pass F (Dana Point to Oceanside Harbor) 19:37-19:51

| Source Geospatial Form: tabular digital data | Type of Source Media: digital files

GPS base stations solutions were estimated with respect to the GPS Continuously Operating Reference Station (CORS) at Pinyon Flats, CA.

DESIGNATION: PINON 1 PGGA CORS ARP

CORS_ID: PIN1

NGS PID: AF9708

| Type of Source Media: online

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 50Hz 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 April 13, 2008, were compared to kinematic GPS points collected along the E. Pacific Coast Hwy near

Laguna Beach. Data collected on April 12, 2008, 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.

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.