Ashtech ProFlex 500 GNSS Teams with FieldSens 3-D Undersea Utility Geopositioning
The Ashtech ProFlex 500 receiver has been selected to provide GNSS position data to the recently introduced FieldSens underwater utility mapping system from Optimal Ranging Inc. FieldSens is a faster and more accurate means of locating underwater utilities than conventional methods because the FieldSens towed unit only needs to be in the general vicinity of the utility line to provide accurate 3-D mapping of the line. The FieldSens technology is based on the optimization of data from many sensors, including ProFlex 500 GNSS data, a pressure sensor, 3-axis digital compass, and pitch and roll, against a physical model of the magnetic field expected from the utility line. The FieldSens method eliminates the need to bring the measurement equipment to specific points along the utility cable or pipe in order to validate position. Conventional instruments must find the peak or null in the signal in order to confirm pipeline or cable position. The underwater towed FieldSens calculates position including bottom depth, utility depth, and depth of cover measurements, with each value is accompanied by a confidence interval.
The towed rig, which can also be fixed-mounted to the vessel for shallow water applications, receives the ProFlex 500 positioning data stream via Bluetooth. Additional Bluetooth streamed data includes data from the vessel’s depth sounder and length of the automated tow cable.
The Ashtech ProFlex 500 GNSS receiver was selected for its excellent positioning performance, very flexible NMEA-like application interface, integrated GSM modem with NTRIP network corrections, robust design, and quick change camcorder-type battery, according to Jim Waite, president of Optimal Ranging.
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