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www.seadiscovery.com angular resolution in the along track and 0.7 degrees in the across whilst allowing 200 degrees of coverage with 800 beams per ping. Whilst effective on a surface vessel, the depth rating of 6000 m ensures the unit is capable of working in even the most extreme situations whether on AUV or ROV. The EM2040 is capable of resolving objects in the sub-decimeter range. This means that in order for several lines to syn- chronise cleanly, extremely accurate subsea positioning is required. In the past this was done solely usingacoustics however this will never meet the sub-decimetre level required. High amounts of interpo- lation and post processing will be required leading to an increase of error margins; but the use of an inertial navigation system integrated with a subsea positioning system canprovide the precision required. It was decided to use the KONGS- BERG Hydro Acoustic Inertial Navigation system (HAIN), which uses the KONGSBERG HiPAP sys- tem along with an Inertial Motion Unit (IMU), Doppler Velocity Log (DVL) and Digiquartz depth sensor to achieve unrivalled subsea posi- tioning. By utilising an advanced IMU that can give extremely accu- rate heading, we can remove a great deal of the calibration work previ- ously required on such a system. For this project we chose a HiPAP 350PI system with an integrated IMU. Despite it being a portable system the HiPAP was still capable of utilising the new Cymbal tech- nology pioneered by KONGS- BERG, giving far greater range reso- lution and improved Signal to Noise Ratio (SNR) performance. With the integrated IMU the need for anycalibration is removed allowing for a very fast mobilisation and more effective use of vessel time. The mobilisation of the equipment andROV took just 18 hours. Providing accurate results quickly With multibeam data the acquisi- tion is normally the easy part; it isthe processing that is more complex. Backing out pitch, roll, heading, latency, navigation and sound veloc- ity errors can be incredibly time Figure 2 MTR#2 (66-81):MTR Layouts 2/22/2012 10:14 AM Page 73