Predicted tides were applied to the data in real time: at Tutuila, Pago Pago (170000) predicted tides were used with no corrections; at Rose Atoll, Pago Pago tides were used with +0.1 hr time correction and a range ratio of 0.92; and at Swains Island, Pago Pago predicted tides were used with a -0.5 hr time correction and a 1.12 range ratio.
Horizontal accuracy is 20m (no differential GPS correctors applied), vertical accuracy is depth dependent (~1% of water depth), WGS84 datum. These data are not to be used for navigation. Depths mapped range from 1 - 300 m. The AHI was deployed from the NOAA Ship Hi'ialakai and concurrent mapping was done using Simrad EM300 and EM3002D sonars aboard the ship; metadata for HI-06-02 are submitted separately.
The AHI's equipment serial numbers, software versions and sensor configuration settings are as follows:
RESON 8101-ER multibeam echosounder Transducer serial #: 201004 Firmware, dry: 8101-2.07-2D4D Firmware, wet: 8101-1.06-2F6B
R/V AHI POS/MV Model 320, version 3 PCS serial #: 474 IMU serial #: 203 Controller software: v 2.1 and 2.21* PCS Firmware: 2.16
Seabird SBE19 CTD: Serial #: 3029
*The AHI's POS/MV was moved from the launch to the ship each day during part of this cruise. On the evening of Feb 17th (local time) the ship's POS/MV started continually rebooting. With assistance from Applanix we determined that the problem was isolated to the PCS, the rack-mounted controller box. We moved the PCS from the AHI to the ship and were able to continue to survey. Because the IMU was not moved no recalibration was required. The PCS was moved between the ship and the AHI daily for several days, allowing the ship to survey at night and the AHI to survey during the day. The major aspect of the move was that the power supply for the IMU is not compatible between the ship and the AHI and had to be changed out each time the unit was moved. The settings for each vessel's configuration were saved to disk and reloaded at the beginning of each session. This continued until Feb 24th when the ship's replacement unit arrived. Another problem that came to light near this same time was that some times the POS/MV would provide two different date stamps for the data, the time reported on the screen did not agree with the one reported out the Ethernet data stream. When this was noticed on Feb 26th new firmware (v 2.21) was loaded immediately and corrected the problem.
R/V AHI Lever Arm Distances and Alignment Offsets: The R/V AHI Reference Point (RP) is defined to be the intersection of the vessel's centerline, the cabin deck and the bulkhead immediately aft of the transducer. This is marked by a punch in the deck weld at that location. Positive X means the point is forward of the RP, positive Y means the point is to starboard of the RP, positive Z means the point is below the RP. The loaded waterline is defined as the intersection of the vessel's performance wing with the hull at the transom.
POS/MV Settings: RP to IMU, m 0.80 0.00 0.08 RP to Primary GPS(port),m 0.85 -0.50 -2.29 RP to Vessel, m 0.16 0.00 0.77 IMU w.r.t. Ref. Frame, deg 0.00 0.00 0.00 RP to Heave lever arm, m -0.67 0.00 0.00 RP to Sensor 1(MB transducer), m 0.16 0.00 0.77 RP to Sensor 2 0 0 0 Sensor 1 rotation Ref. Frame, deg 0 0 0 Sensor 2 rotation Ref. Frame, deg 0 0 0 Antenna Baseline Distance: 1.229
ISS2000 Settings for RESON DTC: Roll Bias, deg 0.15 Pitch Bias, deg 0.025 Gyro Bias, deg 0.0 Transducer depth, m 0.62
Resource Description: Reson 8101ER Multibeam Sonar Data from Cruise AHI-06-02 (R/V AHI)
These data are also archived through NOAA's National Geophysical Data Center at <http://www.ngdc.noaa.gov/mgg/bathymetry/multibeam.html>
Data Format - Generic Sensor Format, as described in <http://www.ldeo.columbia.edu/res/pi/MB-System/formatdoc/gsf_spec.pdf>