Hugh Roarty

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The Worlds First Triple Nested HF Radar Test Bed
for Current Mapping and Ship Detection
Hugh Roarty Scott Glenn Josh Kohut Rutgers
University Don Barrick Pam Kung CODAR Ocean
Sensors
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Rutgers University Coastal Ocean Observation Lab
Operate New Jersey Shelf Observing System
1) L-Band and X-Band satellite receivers 2)
Nested Multi-static HF radar array 3)
Long-duration fleet of autonomous
underwater gliders
CODAR HF Radar Operations with the New Jersey
Shelf Observing System
1998 - First 25 MHz system test 1999 - 25 MHz
system setup for continuous operation 2000 -
First 5 MHz system deployed - Begin
testing 25 MHz Bistatic Augmentation 2001 -
Operational 5 MHz network with four systems
- Deploy 25 MHz bistatic transmitting buoy
- Begin testing 5 MHz Bistatic
Augmentation 2002 - Implement multistatic/multi-fr
equency network - 2 25 MHz
systems - 4 5 MHz systems 2003 -
Deploy 5 MHz bistatic buoy - Help extend
coverage along entire Northeast coast
as part of NEOS Currently operate 10
systems from Wildwood, New Jersey to
Nantucket, Ma.
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CODAR Ocean Sensors, Ltd.The Leader in HF
Surface-Wave Radar Ocean Monitoring

• Company principals have been continuously
  involved in HFSWR for 35 years
• Patented CODAR Hallmarks
• Compact antenna system --small footprint offers
  unobtrusive coastal presence
• Unmanned, real-time operation
• Low power -- both radiated and required input
  supply
• GPS-synchronized multiple-radar and multi-static
  operation at same frequency
• Currents mapped to 200 km with Long-Range
  backscatter SeaSondes
• Bistatic augmentation by CODAR demonstrates
  coverage extension to 330 km
• Over 150 CODAR SeaSondes manufactured and sold --
  85 of all HFSWRs
• Systems logged over 4 million operating hours to
  date
• Recent "Dual-Use" objectives being pursued to
  examine ship detection/tracking
• Robust, multiple-look at same target defies
  evasion
• HFSWR is CODAR's only product -- provides us
  unparalleled focus of direction

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Applied Mathematics, Inc.
SHIP-TRACKING SAMPLE
SHIP-TRACKING SAMPLE
COMPANY BACKGROUND
COMPANY BACKGROUND

• Extensive experience in development, at sea
  testing, and analysis of ship detection and ship
  tracking algorithms for US Navy and the United
  Kingdom Royal Navy
• Have provided on site technical support for 28
  years in search and ship tracking tactics to
  Commander Submarine Development Squadron TWELVE,
  the tactical development agent for the Submarine
  Force
• Developed over past twenty-five years search and
  tracking computer programs (called tactical
  decision aids) for real time use on board
  submarines
• Developed ocean current data assimilation and
  area of uncertainty tracking algorithms for US
  Coast Guard Search and Rescue applications

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OBJECTIVES

• Test new transmission waveforms
• Multistatic SeaSonde data from the network will
  be collected, however, this initial set of tests
  will focus on analyzing the backscatter data only
• Test different detection algorithms
• Test the sensitivity of the MUSIC direction
  finding algorithm to ideal versus measured beam
  patterns for hard targets
• Define the parameters to optimize dual-use ship
  tracking and current mapping with a Codar
  SeaSonde

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HF RADAR NETWORK
180 km
RUTGERS
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Ship Tracking Throughout Rutgers HF Radar Network
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60 Transits of Oleander in 2004
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5 MHz Loveladies, NJ
New Jersey Installations Used for Oleander Tests
5 MHz Sandy Hook ,NJ
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Detection Algorithm

• Simultaneous multiple sliding window
• FFTs in Doppler processing
• Two types of background calculation ---
• median and IIR
• 3D background (Time, Range and
• Doppler) varying with sea echoes
• Thresholding of peaks --- local SNR of
• monopole or at least one of the two
• dipole antennas have to be above the
• threshold
• MUSIC algorithm used to determine
• bearing
• Bearing precision determined by SNR
• (1/sqrt(SNR))

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Pepper Plots

• All targets detected 9 dB above background

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Ship Tracking Algorithm

• A Kalman Filter provides a recursive solution to
  the least squares problem.
• Assumptions include linear target motion and
  normally distributed measurement errors.
• Tracker inputs are time radar transmitter and
  receiver positions range, bearing, and range
  rate and range, bearing, and range rate
  uncertainties.
• Tracker outputs are target position velocity
  and estimates of position and velocity
  uncertainties (covariance matrix).
• Target Maneuver Test a statistical test is used
  to estimate whether a combination of two straight
  tracks fit the data better than a single straight
  track.

Oleander Constant Course and Speed Tracker
Solution Using CODAR Detections from 23 November
2002
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Tx
Rx
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RESULTS
SMALL BOATS

• SeaTow 41 41 length
• SeaTow 25 25 length

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SeaTow 41
Loveladies 5 MHz
13 nm
Tuckerton 5 MHz
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SeaTow 41
Boat Speed 25 knots
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SeaTow 25
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SeaTow 25
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Present Focus

• Hardware Improvements
• 13 MHz Codar SeaSonde, December 2004
• 13 MHz Codar Superdirective System, July 2005
• Software Improvements
• SIFTER Algorithm

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Sandy Hook Facility March 2004Continuous
Operation Since July 2001
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• Sandy Hook
• Test Bed
• Present Day
• 25 MHz system installed March 2004
• 5 MHz Transmit Antenna moved 1 wavelength back
  from shoreline
• 13 MHz System Installed December 2004

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25 MHz Tx/Rx
5 MHz Tx
13 MHz Rx
5 MHz Rx
13 MHz Tx
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Three Frequency Coverage

• 5 MHz
• 13 MHz
• 25 MHz

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Pattern Measurement
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25 MHz System in Clear Environment
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25 MHz HOSR
Pattern Measurement
Radial Distribution
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Low Pass
Hook
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• Sandy Hook
• Test Bed
• Future
• 13 MHz SuperDirective System Installation July
  2005

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13-MHz Heptagonal Array Being Built and Tested at
CODAR
SuperDirective System

• 23-foot (7-m) high mast
• 2 masts 21 dB directivity over ground
• -32 dB efficiency
• The gain of a directional antenna with the
  footprint of an omni directional antenna

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Future Work

• Utilize AIS signal to ground truth multiple ship
  tracks
• New and Different Targets

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Automatic Identification System (AIS)

• Required on vessels of
• 300 gross tonnage or greater,
• Length Over All (LOA) over 20 meters, or
• carries more than 50 passengers for hire

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GPS Track of RV Hatteras April 5-21, 2005
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GPS Track of Oceanus April 7-25, 2005
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Transits of Oleander in 2005
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How did the move of the Transmit Antenna Affect
Radial Coverage?
5 MHz Rx
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5 MHz Transmit Antenna Move
BEFORE
AFTER
25
50
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Radial CoverageApril 2005
Radial CoverageNovember 2004
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13 MHz HOMR
Pattern Measurement
Radial Distribution
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Simulated Bearing Error with Distorted, Measured
Antenna Patterns Compared with Real Ship Bearing
Data

• Simulated points follow power law
• Compared to
• Ship detections at lower SNRs may differ
  because
• Noise peaks are mis-identified as ships
• "Noise" near peak contains ship signal,
  i.e., it is too high

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5 13 MHz Receive Antennas in Cluttered
Environment
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Simulated Bearing Error with Added Bias from
Improper Antenna Pattern Compared with Real Ship
Bearing Data

• For Simulation
• Measured distorted pattern inputted
• Ideal pattern used to recover echo
• Expected power-law fit is offset by 16
• Ship is also offset when inappropriate ideal
  pattern is used

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Oleander DetectionsFebruary 28, 2005 Outbound
128 point FFT 6 dB Threshold
256 point FFT 7 dB Threshold
512 point FFT 8 dB Threshold
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SuperDirective Beam Patterns 360 degree coverage

• Blue curve is theoretical pattern for 7-element
  array
• Red results from use of measured transponder
  pattern

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• Developed by Mission Research Corporation (MRC)
• Originally developed for ROTHR (Relocatable Over
  The Horizon Radar)
• SIFTER rejects peaks that do not move in a
  consistent way
• SIFTER finds smoothest distribution of
  scatterers that reproduces HFSWR or ROTHR
  measurements
• Targets appear as localized peaks

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SIFTER Results
Cross Spectra after SIFTER
Cross Spectra before SIFTER