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The Santa Barbara Channel Experiment (SBCX)

Radar Data

The SBCX had the benefit of being under surveillance by two sets of radars. The first was the radar onboard R/V FLIP, and the second was the NAWC surveillance radar. FLIP radar contacts were recorded on a handwritten log, which was then transcribed by Steve Wales of NRL. His transcription can be found here. (Note: Julian Day 96 is April 6, 1998)

The NAWC Sea Range was instrumented with three surveillance radars, located at Laguna Peak, San Nicols Island, and Santa Cruz Island. Only data from the Laguna Peak (near Point Mugu) and Santa Cruz Island radars were relevant to SBCX. The Laguna Peak radar was having problems throughout the experiment, so most tracking data was derived from the Santa Cruz Island radar.

Annotated Radar Summary Map

The blue dotted lines in the map above indicate shipping channels to and from the Ports of Los Angeles and Long Beach. Most of the radar contacts fell within these channels. Red dots correspond to oil drilling platforms in the Channel. The black dotted line from Santa Cruz Island radar denotes a radar shadow zone. This sector blanking was put in place by NAWC so the Santa Cruz Island radar would not interfere with another radar (presumably Oxnard airport) in Ventura County, California. Unfortunately, the FFP array is inside the shadow zone, so radar contacts could not be tracked in this area.

Digital radar data was archived by NAWC and furnished to NRL on 9 track, 6250 bpi tapes. Problems with equipment yielded temporal gaps in the radar coverage. Consequently, some blocks of time are missing.

Steve Wales (NRL) wrote a FORTRAN program (ship_tracker.f) to process the digital radar data from NAWC, arranging it into a series of tracks. Each track is keyed by a contact number, which lists the ship's position, course, and speed. Only ships which were in contact for longer than 30 minutes, and which were traveling between 5 and 35 knots were included in the tracker output. The track output is listed in the table below.

Radar Julian Start Date Start Time Julian End End Time Tracker
File Day YYMMDD UTC HH:MM:SS Day Date UTC HH:MM:SS Output
01 98 980408 20:41:23 99 980409 12:35:43 sbcx01.ships
02 99 980409 14:24:28 100 980410 04:32:55 sbcx02.ships
03 100 980410 05:14:39 100 980410 20:40:01 sbcx03.ships
04 100 980410 21:21:46 101 980411 12:48:17 sbcx04.ships
05 101 980411 13:43:36 102 980412 08:41:16 sbcx05.ships
06 102 980412 09:12:30 102 980412 23:03:47 sbcx06.ships
07 102 980412 23:27:33 103 980413 17:36:45 sbcx07.ships
10 104 980414 01:00:46 104 980414 12:25:13 sbcx10.ships
11 104 980414 20:16:18 105 980415 13:18:22 sbcx11.ships
12 105 980415 13:24:59 106 980416 06:28:29 sbcx12.ships
21 125 980505 15:55:44 126 980505 08:19:30 sbcx21.ships
22 126 980506 08:47:58 127 980506 00:11:49 sbcx22.ships
23 127 980507 01:22:27 127 980507 17:00:30 sbcx23.ships


Ship Tracker Output Format

The format of the ships files listed above is straightforward. The first nine lines are common to each file, indicating the decimal lat/long coordinates of various features within the Santa Barbara Channel. Note the listed location of the FFP array was based on initial (inaccurate) measurements; the true location has since been refined.

LagPk -1.0000000 34.1074287 -119.0666930 Laguna Peak Radar
SNI -1.0000000 33.2476743 -119.5257477 San Nicols Island Radar
SCI -1.0000000 33.9944903 -119.6326597 Santa Cruz Island Radar
FLIP -1.0000000 34.1169167 -119.3683167 Deployed position of R/P FLIP
FFP -1.0000000 34.1102933 -119.3306333 FFP Array Center
GRACE -1.0000000 34.1797222 -119.4688889 Oil Drilling Platform Grace
GINA -1.0000000 34.1172222 -119.2772222 Oil Drilling Platform Gina
GILDA -1.0000000 34.1822222 -119.4194444 Oil Drilling Platform Gilda
GAIL -1.0000000 34.1250000 -119.4011111 Oil Drilling Platform Gail


The remainder of the tracker output file is sectioned by contact number. The first three lines of sbcx01.ships is given as an example. A ship may have more than one radar contact number, especially if it passes through the sector shadow zone shown above. One contact number may be assigned before the shadow zone, and a different contact number when the ship emerges from the other side of the shadow zone.

Track Number Decimal Time Decimal Latitude Decimal Longitude Radar X Radar Y Range from FFP Bearing from FFP Target Speed Target Course
(nautical miles) (degrees) (knots) (degrees)
3498.862966933.9342727-118.902966739539.9-19441.923.79116.1820.51-93.24
3498.863798833.9339266-118.911160038782.6-19483.423.43116.6726.85-44.66
3498.865229633.9449389-118.924064037584.7-18266.822.56115.9220.30-81.97

Parse Tracker

One objective was to merge this radar data with the acoustic data generated from the FFP array. Radar data would provide confirmation of surface ship localization using acoustic data from the FFP array. Another program (parse_tracker.c) was written to: Usage of this program can best be described through an example. The program was written for Red Hat Linux, but should compile with little modification under other flavors of UNIX. To compile parse_tracker, you will need the parse_tracker.c source file, convert_datum.c, convert_datum.h, and the Makefile. Compile the program by typing:

% make parse_tracker

or, download the pre-compiled binary (Red Hat v6.2, i386) here. As an example, attention will be focused on a section of time during run A/X 2, when the USS Acoustic Explorer was stationary at a point 15.3 km from the FFP array, and a single Evergreen Lines cargo ship was moving southeast, toward the Port of Los Angeles:

% parse_tracker "102 01:45:00" "102 01:50:00" sbcx05.ships x2-15-ships

parse_tracker prints out the following:

You have requested the following:
Start time: 102.072917 102 01:45:00.00
Stop time: 102.076389 102 01:49:60.00
The file [sbcx05.ships] has the following time bounds:
Start time: 101.921603 101 22:07:06.51
Stop time: 102.361971 102 08:41:14.28
There is 1 target which fall under within the specified time limits.
Target ID: 324 Number Track Lines: 3


The program generates four output files. The first, x2-15-ships.102.076359.324.log converts the tracker output to metric units. This file can be used to determine necessary parameters for MFP localization.

Decimal Date Decimal Seconds Julian Date UTC Time Track Number UTM X Coordinate (m) UTM Y Coordinate (m) FFP Range (nautical miles) Corrected FFP Range (meters) Degrees bearing from FFP Corrected bearing from FFP (Degrees) Corrected bearing from FFP (Radians) Target speed (m/sec) Target course (Degrees)
102.073593 8819158.44 102 01:45:58.44 324 289534.249156 3767168.728184 [ 5.76 10686.19] (153.70000 154.94040) -1.133424 rad 12.004514 m/sec 118.020000 deg
102.074561 8819242.06 102 01:47:22.06 324 290408.303115 3766675.466096 [ 6.21 11517.99] (150.79000 152.03980) -1.082799 rad 12.225867 m/sec 117.340000 deg
102.076359 8819397.40 102 01:49:57.40 324 292072.458388 3765762.489131 [ 7.09 13146.00] (146.23000 147.49422) -1.003463 rad 8.313589 m/sec 108.170000 deg


"Corrected FFP Range" indicates the correct range to the center of the FFP array, in meters. "Degrees bearing" assumes True North is 0 degrees, while "Corrected bearing from FFP" assume True North is pi/2 radians. The remaining three output files (x2-15-ships.102.073593.324.start, x2-15-ships.102.076359.324.track, x2-15-ships.102.076359.324.stop, are designed to be fed into the plot_bath bathymetric plotting program. With the locations of R/P FLIP, the oil rigs, and the radars in the files (flip_loc, oilrig_loc, and radar_loc), one can type:

% plot_bath sbcxvect.utm sbcxbath.utm *loc x2-15-ships.*.324.{start,stop,track}

The following plot should appear:
X/2-15 Radar Contact Map

The radar track appears as a green and red dot, connected by a blue line. On the blue line, the green dot indicates the beginning of the track, while the red dot indicates the end of the radar track. The Evergreen container ship is moving along the Eastbound shipping lane, passing through UTM X coordinate 290000, bound for the Port of Los Angeles.

Isolated Blue dots indicate the location of the radar stations. Isolated Red dots are oil rigs. The large isolated green dot is FLIP, while the small isolated green dot is the FFP array. UTM X coordinates are listed on the bottom horizontal axis.

With this information, it should be possible to generate radar track plots for any of the available time intervals and targets. For example, a plot of all of the radar contacts during run A/X 2 can be found here.

Last updated: 000617
Comments/Questions: pmd@alum.mit.edu
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