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

Create custom data files by choosing data area, product type, map projection, file format, datum, etc.

Simple download of data files.

Date that the source FGDC record was last modified.

Converted from FGDC Content Standards for Digital Geospatial Metadata (version FGDC-STD-001-1998) using 'fgdc_to_inport_xml.pl' script. Contact Tyler Christensen (NOS) for details.

Partial upload of Positional Accuracy fields only.

Partial upload to move data access links to Distribution Info.

air and ground GPS files

base station coordinates Easting, Northing, HAE in NAD83, Zone 11 (Latitude, Longitude):

Seal Beach (SEAL) = 399190.391, 3733584.061, -27.27 (N 33 44 15.03843, W 118 5 17.76522)

San Onofre (SANO) = 447430.242, 3693036.862, -5.18 (N 33 22 31.08775, W 117 33 54.54417)

Scripps Pier (PIER) = 476092.938, 3636525.033, -25.376 (N 32 51 59.68647, W 117 15 19.93179)

Point Loma (LOMA) = 477399.589, 3614791.248, 90.939 (N 32 40 13.99744, W 117 14 27.74866)

| Type of Source Media: digital file

raw lidar data from ALTM 1225 (all times UTC)

29105

Pass A (Carlsbad to Long Beach) = 20:28-21:06

Pass B (Long Beach to Dana Point) = 21:09-21:52

Pass C (Dana Point to Long Beach) = 21:54-22:08

Pass D (Long Beach to Carlsbad) = 22:10-22:18 and 22:26-22:50

Pass E (Carlsbad to Dana Point) = 22:53-23:07

Pass F (Dana Point to Carlsbad) = 23:10 to 23:24

2 Calibration Passes = 22:21-22:26

29205

Pass G (Carlsbad to Mexico) = 21:10-21:46

Pass H (Mexico to Point Loma) = 21:47-21:54

Pass I (Point Loma to Mexico) = 21:56-22:03

Pass J (Mexico to Carlsbad) = 22:04-22:39

Pass K (Carlsbad to La Jolla) = 22:41-22:55

Pass L (La Jolla to Carlsbad) = 23:06-23:21

2 Calibration Passes = 22:58-23:03

| Type of Source Media: digital file

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, by shoreline pass, 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.

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). Parse the 9-column lidar point file into 3.75-minute

quarter-quadrangle components. Convert UTM Easting and Northing to geodetic latitude and longitude with respect to

the GRS80 ellipsoid. The conversion was computed using the TMGEOD and TCONPC fortran subroutines written by T.

Vincenty (NGS). Each record contains 9 columns of data: time tag (seconds in the GPS week),first return Latitude,

first return Longitude, first return NAVD88, last return Latitude, last return Longitude,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). Latitude and longitude are in decimal degrees with nine significant digits to retain the 0.01m

resolution of the UTM coordinates. West longitude is negative and north latitude is positive. The UTM quarter-quad

files were re-organized into latitude delineated files. UTM quarter-quads files that were delineated by the same

upper and lower latitude bounds were concatenated. The lat-long files were named by the month-year of the survey

(e.g. sep04) and the lower latitude bounding the quarter-quad. Processing occurred 20051018-20060222.

Created initial metadata

The NOAA Office for Coastal Management (OCM) received files in ASCII format. The files contained LiDAR intensity

and elevation measurements. OCM 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.