Quality Assurance and Quality Control Processes for Current Measurements From USCG ATONs Jennifer Dussault Qartod II February 28,2005

PORTS® is a NOAA program that provides mariners with accurate information to improve safety and efficiency of maritime commerce

A TYPICAL PORTS ® SITE PROVIDES:  Predicted and observed water levels  Meteorological information including wind speed and direction, barometric pressure, air temperature  Predicted and observed currents  Water density, salinity/temperature  Access to the data in graphic and text format via internet, and voice All data are updated at 6-minute intervals All data are quality controlled CH-PORTS

WHY PUT CURRENT METERS ON ATONs ? Underwater cable to shore has long been a PORTS operations weak link Maritime community requires current information within navigation channels

“Not to Interfere” CONSIDERATIONS  Deployed/recovered with buoy on station  Entire package removed prior to ATON servicing  All similar metals and coloration  Minimal alteration of buoy profile and characteristics

 Total package weighs ~ 195 lbs  < 0.1” estimated lowering of buoy optics  < ½ deg estimated buoy tilt  Completely battery powered USCG Approval

THE CLAMPARATUS

DAVID TAYLOR TESTING November 2002 All Nortek Aquadopps are tow-tested at David Taylor before operational use, as required by CO-OPS policy

The mean difference using bin two was m/s and the mean difference using bin four was m/s

BUOY “2C” Prototype Installed 17 December 2002

BUOY 2C - DIRECTION One month of current meter data were compared to predictions from a station ¾ mile away Compass problem became obvious immediately

COMPASS CALIBRATION IN THE LAB Nortek designed and installed a firmware enhancement which allows compass calibration Several tests were performed in the lab and on a buoy at the USCG yard

COMPASS CALIBRATION IN THE FIELD

Encouraging  Flood and ebb occur together, with similar time/direction characteristics  Largest differences occur at the change of tide when the currents are weak and variable. Examine 5 day slices of directions Black = Bottom Mount Red= ATON Blue = |difference| AFTER CALIBRATION Discouraging  There is no clear pattern, the ATON is not always higher/lower on flood/ebb.

Mar 18 th – Apr 6 th 2004 Bottom Mounted RDI 600 KHz WH 1m bins ATON Mounted Nortek 1 MHZ Aquadopp 1 m bins PINEY POINT ATON vs BOTTOM MOUNT CURRENT COMPARISON

3 bins: surface (3.5 m/11.5 ft) mid depth (9.5m/31.2 ft) bottom (15.5 m/44.3 ft) Speeds compare very well, within anticipated error of individual instruments No obvious bias in ATON Mean difference ~ 3cm/s = 0.06 knots

ATON measurements are noisier at all levels due to buoy motion. ATON has on the order of 10X larger vertical velocity in the uppermost bins.

Seeking a parameter that correlates well with the difference in direction between the Bottom Mount and ATON. This is the mid depth signal.

Direction Difference vs Buoy Heading

Direction Difference vs Current Direction

Direction Difference vs Buoy Pitch

FREEPORT, TX ATON vs BOTTOM MOUNT CURRENT COMPARISON January 13 – May 4, 2004 Bottom Mount RDI 600 KHz WH 1m bins ATON Mount Nortek 1 MHZ Aquadopp 1 m bins

Again speeds compare very well, with no obvious bias Mean difference ~ 3 cm/s = 0.06 knots

Again focusing on direction Black = Bottom Mount Red = ATON Blue = |difference|

Difference in direction between the Bottom Mount and ATON clearly decreases with increasing current speed. Mouth of the Freeport River is in the Gulf of Mexico:  Not tidally dominated  Large directional differences at times current reversal

R/V Fay Slover moored at 2CH One complete tidal cycle May 2004 Hull-mount RDI 600 KHz WH 1 meter bins ATON Mount Nortek 1 MHZ Aquadopp 1 m bins BUOY 2CH ATON vs HULL-MOUNTED CURRENT COMPARISON

GPS COMPASS CALIBRATION IN THE LAB Goals: Rotate GPS compass and Nortek to determine the effectiveness of the Nortek compass calibration algorithm Evaluate potential for GPS compass calibration of the Nortek November 2004, and February, 2005 Thales GPS Compass 10 Hz compass sampling rate, 1 sec average Nortek 1 sec compass sampling rate

GPS COMPASS TEST IN THE LAB, PART I

GPS COMPASS TEST IN THE LAB, PART II

GPS COMPASS TEST ON ATON 14 Large differences correlate to times when the buoy was turning quickly GPS and Nortek were not aligned (261 degree offset) Plan another test for an entire tidal cycle Make mount to raise GPS antenna above the ATONs solar panel Plan to study how slow you need to rotate the GPS to reduce error

QA/QC WHAT’S NEXT ? Refine compass calibration procedure Find a method for removing “fake w” Continued GPS testing Long term comparison of ATON and bottom mount at an existing PORTS station

Ocean Systems Test and Evaluation Program NOAA’s Ocean Service Center for Operational Oceanographic Products & Services

ACKNOWLEDGEMENTS USCG 5th District ATON Group OceanScience and Nortek USA Maryland Port Administration Field Crew from the CO-OPS Field Office in Chesapeake, VA Old Dominion University – CCPO Fugro GEOS – Freeport LNG