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SPRINT-Nav Installation and Integration

21 June 2021


When installing/integrating a SPRINT-Nav onto a vehicle, there are many factors to consider/plan to ensure the system is operational and performs to the required specification.

Installation location 

SPRINT-Nav can be installed at any convenient location on the vehicle. However, to gain optimal performance from the system, identify a location to install the SPRINT-Nav that conforms as closely as possible to the following criteria:

  • The location must not be subject to excessive vibration or impulse shock.
  • The location must not exceed the environmental limits for temperature (operating temperature -5 to 50°C / storage temperature -25 to 55°C).
  • The location must provide a mounting surface that is of sufficient strength to support the weight of the SPRINT-Nav safely and without flexing.
  • The location must provide access for power and communication connections.
  • There must be sufficient space to allow easy access to install the SPRINT-Nav.
  • Do not store tools, equipment or chemicals where they can damage the SPRINT-Nav or the connection cables.
  • Make sure the SPRINT-Nav and its connection cables do not cause an obstruction to personnel operating in the area.
  • Do not use a location where the connection cables are likely to suffer damage from mechanical stresses or chemical attack.
  • The location must provide line of sight to the seabed for all 4 Syrinx DVL transducers abiding by the clearance levels:
    • This includes 15° clearance around the direction that is orthogonal to the transducer face. The transducer face is orientated at 30° azimuth from the vertical (downward) direction, with each beam at a 90° offset in yaw respective to one another, and all beams rotated 45 degrees in yaw from the forward mark.
    • The SPRINT-Nav should be mounted at the greatest distance possible away from the seabed. This is to offset the minimum altitude of operation of the SPRINT-Nav of <0.4 m. If the SPRINT-Nav can be mounted 0.4 m or greater above the bottom of the vehicle with clear line of sight, bottom lock should rarely be lost even if the vehicle settles on the seabed.
  • The orientation of the SPRINT-Nav is also important and can affect performance in certain scenarios.
    • For most operations, the desired orientation is to line up the SPRINT-Nav forward mark (label or machined grove on housing) with the forward heading of the vehicle.
    • For following pipelines where altitude measurements above the pipe are very important, the SPRINT-Nav can be rotated by 45 degrees so that beams then face forward, aft, port and starboard rather than inter-cardinal directions. This will result in the forward and aft beams being directed onto the pipe surface. Mounting angles will need to be adjusted appropriately in this instance.

Mounting

The SPRINT-Nav can be installed in any convenient orientation with respect to the vessel’s body frame. Compensate for any misalignment between the SPRINT-Nav and the vessel by carefully measuring the mounting angles and entering them in the SPRINT-Nav system.

The SPRINT-Nav has a set of eight mounting holes (a further four alternative mounting holes are available) on the outer mounting ring of the unit. In addition, there a set of three-dowel alignment holes.

Alignment

The nominal alignment of the SPRINT-Nav to the vehicle frame (FWD and STBD) is engraved on the top endcap.

If it is not possible to mount the SPRINT-Nav within the limits described above for coarse alignment or if you wish to mount the SPRINT-Nav at other angles with respect to the reference axes on the vessel, ROV or platform, the mounting angles must be measured and configured.

For the SPRINT-Nav to provide accurate attitude and positions with respect to the vehicles reference frame, any misalignment between the SPRINT-Nav and vehicle reference frame must be corrected by determining and applying mounting angles in the SPRINT-Nav system.

SPRINT-Nav Instrument Frame

The SPRINT-Nav system has two types of lever arm and mounting angle measurement references, vehicle frame and instrument frame:

  • Vehicle Frame: SPRINT-Nav IMU and sensor lever arms and mounting angles relative to vehicle CRP/Frame (from vehicle CRP/Frame).
  • Instrument Frame: sensor lever arms and mounting angles relative to SPRINT-Nav IMU (from measurement point of the sensor assembly).

The instrument frame measurements for the SPRINT-Nav are stored as the factory default within memory, therefore when applying lever arms and mounting angles to the SPRINT-Nav from vehicle CRP/Frame, the user simply applies the new values to the SPRINT-Nav IMU and the system automatically calculates and applies this to the SPRINT-Nav sensors (Syrinx DVL and pressure sensor).

Interfaces and Connections

Prior to installation, SPRINT-Nav system interfaces should be planned to avoid any sensor/system incompatibilities therefore causing delays in the system becoming operational ready.

  • Time System: Depending on what navigation requirement is (Dynamic/Construction survey to ROV guidance) will determine what type of time system is required:
    • ZDA + 1PPS
    • ZDA only
    • No Time Sync
  • Position Aiding:
    • USBL (PSIMSSB of GGA telegram)
    • LBL Range Aiding (Fusion 2)
  • Sound Velocity
    • External sensor feed into the SPRINT-Nav system (Subsea or Topside connection)
    • Manual or Derived sound velocity for ROV Guidance
  • SPRINT-Nav output messages
    • Survey software (EIVA)
    • Multibeam
    • Vehicle Guidance

Whatever the sensor/systems interfaced with the SPRINT-Nav, ensure all message formats are compatible and available prior to installation to avoid issues and delays.

Cabling

The system cabling must be carefully planned prior to installation to avid issues. Subsea cables can be costly, and time consuming to correct or replace during the installation phase.
Consideration should be given for any serial cable run length, as this could lead to data corruption if the length exceeds RS232/485 limits, particularly the serial connection between the SPRINT-Nav system and the ROV (de) multiplexer is excessive for a 115,200 baud rate RS232 serial link then alternate interfaces should be planned to make sure the data is not corrupted, such as Serial to Ethernet or RS232 to RS422/485 converters. Alternatively, an Ethernet connection to the SPRINT-Nav could be considered. If choosing an Ethernet connection to the SPRINT-Nav, ensure that the vehicle MUX connection support 100Mbit/s.


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