To ensure the SPRINT-Nav provides long and effective service, it is important to carry out general scheduled maintenance.

Cleaning

• Thoroughly wash the instrument in warm clean fresh water to remove accumulations of salt, sand or silt and marine growth, paying particular attention to the electrical connectors.
• Remove any attached cabling or dummy plugs/protective caps and clean the external socket.
• The Seacon connectors are dry mating and do not require lubrication on the connector pins/sockets.
• Dry the instrument and any attached cabling with a clean lint free cloth.
• Replace any attached dummy plugs/protective caps.

Inspection

Regularly inspect the instrument for the following:

• Inspect the pressure relief vent valve.
• Inspect the housing for signs of damage (at full working depth, the instrument housing is at risk of failure if damage is not repaired). The housing is manufactured from titanium and is
• highly resistant to corrosion. Under normal use, the housing should not show any signs of corrosion (maintenance is not necessary).
• Inspect the connectors and cables for signs of abrasion, damage or corrosion and that o-rings are fitted and are in good condition.

Pressure Relief Vent Valve

Check the pressure relief vent valve is flush with the endcap. If the pressure relief vent valve is not flush it could indicate a pressure build-up during previous operations due to a fault developing in the backup battery pack.

Pressure Sensor

It is important that the SPRINT-Nav pressure sensor module is recalibrated annually by returning it to one of Sonardyne’s regional or head offices.

The pressure sensor can be returned separately to accommodate customer operations by following the removal and replacement procedure detailed in the latest SPRINT-Nav user manual. The pressure sensor can be replaced with the supplied blanking plate or another Sonardyne pressure sensor module.

Inertial Sensors

The SPRINT-Nav uses rugged and durable high quality inertial sensors of unrivalled and thoroughly field proven reliability. The sensors are used in systems qualified for the most demanding and safety critical applications and are standard fit for use in the main navigation systems of the majority of today’s commercial and business aircraft. The inertial sensors are maintenance free.

SPRINT-Nav based products do not require re-calibration (excluding the pressure sensor) subsequent to initial factory calibrations unless:

• The unit has been subjected to excessive shock beyond quoted specification.
• Performance re-verification is requested by the customer.

Performance re-verification is often possible in the field without return to factory, contact Sonardyne Support for more information.

Syrinx DVL

The Syrinx DVL integrated into the SPRINT-Nav has a built in self test feature within the WebUI.

If the self test fails for any reason, contact Sonardyne Support.

Scheduled Maintenance

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.

Follow these steps for successful deployment of SPRINT-Nav and SPRINT.

Prior to these deployment steps, SPRINT and SPRINT-Nav systems should be configured with suitable aiding, time synchronisation, installation parameters applied, outputs configured, and the INS algorithm set to use DVL, pressure and position aiding when available.

AHRS settling

The SPRINT / SPRINT-Nav AHRS algorithm will take 10 minutes to settle from start-up.

The AHRS uses the default Latitude set in the SPRINT software, this must be updated to the correct latitude prior to every dive.

The ROV can be moving (early decent) whilst the AHRS settling, once settled the AHRS status LED in SPRINT software will turn green.

INS initialisation

The INS algorithm requires a starting position to initialise, which (In normal operation) is provided by the first accepted USBL position during decent.

Once initialised, the INS LED in SPRINT software will turn green (as well as USBL and Depth). The DVL status LED will turn green when bottom lock has been acquired.

Vehicle descent and INS initialisation sequence

How is  SPRINT-Nav export controlled?

SPRINT-Nav avoids the strict International Traffic in Arms (ITAR) control. Therefore, exporting SPRINT-Nav is simplified compared to separate DVL and INS units. For example, shipping from outside the USA does not require a re-export licence.

Yes, you can post-process SPRINT-Nav data.

All of our inertial products log all required data to perform post-processing, which is done through the post-processing tool Janus.

We developed a very powerful post-processing tool, Janus, which can be used to meet several goals.

Primary functionality is to post-process data logged during the operation to improve accuracy by taking advantage of a backwards-forwards algorithm.

Furthermore, Janus can be used for troubleshooting by inspecting data from the individual sensors such as raw inertial, pressure, USBL, or DVL measurements.

All our inertial products continuously log all required data internally which can be downloaded for post-processing when required. Customers also have the option to log data topside either through SPRINT software or directly from the unit itself.

Yes, all variants of Sonardyne’s SPRINT and SPRINT-Nav systems accept depth aiding from three different sources, Pressure Depth, USBL Depth and External Position Depth.

When providing depth aiding from an external depth sensor, multiple message types are accepted. These are listed in the below table.

The process for setting depth aiding involves the following steps:

1. Set up an input port to accept one of the message types as described above.
2. Set up lever arms.
3. Enable depth aiding.
4. Restart INS.

How to set up a SPRINT or SPRINT-Nav system to be aided by an external depth sensor in SPRINT software is shown below.

1. Click Configure > INS > Depth Input or right-click on Depth Aiding LED.
2. If using the internal pressure sensor continue to Step 3; if not, proceed to Step 4.
3. Select SPRINT-Nav Internal Pressure Sensor; click Apply and then proceed to Step 5.
4. Select Depth Type on the drop-down list and select e.g. DigiQuartz.
5. Select a Depth Input by selecting either PC/LCH Port or SPRINT Port.
6. If the depth sensor is connected via a serial connection on the PC/LCH, select the PC/LCH Port and enter the IP Address for the serial input via the LCH (192.168.179.51:5005) by clicking Configure.
7. If the sensor is connected directly to the SPRINT-Nav, or SPRINT, select and the relevant connection point (C1, T1, T2), as shown below.
8. Click Configure and enter the port configuration settings, see below.
9. Click OK to save all entered settings and return to the Depth window.
10. If required, enter the Surface Offset value in metres. If the systems is on deck and the ambient surface pressure is to be removed from raw pressure depth, clock Auto Set.
11. Enter the Depth Sensor Mounting (from vehicle CPR) lever arm offset from ROV CRP to the depth sensor.
    1. Note: After changing the lever arm the INS algorithm will automatically reset.
12. Click OK to close and save all entered settings.

Contact [email protected] for more information.

Best practices for integrating sound velocity sensor with SPRINT-Nav or SPRNT-Nav Mini.

To achieve the best performance for any acoustic-inertial navigation solution it’s important to provide accurate local speed of sound through water.

To determine the local sound speed is often achieved by fitting a sound velocity sensor (SVS) which directly measures the sound speed.

To get the best performance the SVS should measure sound speed in the same body of water which the DVL experience. The following guidelines will help achieve that:

• The SVS should be fitted in a well-ventilated area, i.e. not within a close area without water flow.
• The SVS should be fitted as close as possible to the DVL head, and always within 30cm of vertical distance.
• The SVS should be fitted in a location that is submerged when the vehicle is emerged, i.e. when e.g. an AUV is surfaced it’s important the SVS is still submerged

Following these guidelines will help ensuring the SVS is measuring the same sound velocity as the DVL is experiencing.

Contact [email protected] for more information.

Can I swap-and-replace between a SPRINT-Nav and SPRINT-Nav Mini?

Yes, SPRINT-Nav and SPRINT-Nav Mini share a subset of Command & Control and output strings, such as LNAV. This means for simple integrations, SPRINT-Nav can be swapped out by a SPRINT-Nav Mini.

However, there are differences between the SPRINT-Nav and SPRINT-Nav Mini which are important to take into consideration.

• SPRINT-Nav Mini uses CRE connectors while the SPRINT-Nav uses Seacon
• SPRINT-Nav Mini utilises a built-in WebUI for configuration, management and troubleshooting while the SPRINT-Nav uses SPRINT which is a dedicated desktop program
• To reduce complexity the SPRINT-Nav Mini uses a much-reduced Command & Control set compared to the SPRINT-Nav
• SPRINT-Nav Mini supports the new Hybrid Navigation output message, HNAV, which provides all required information for navigating subsea vehicles in a single simple message

No, SPRINT-Nav and SPRINT-Nav Mini, are pre-calibrated at our factory. 

Why is the calibration of our SPRINT- Nav hybrid navigators not required and what are the advantages?

To achieve the highest accuracy of any DVL aided INS system it’s critically important to calibrate the DVL beams to the INS system.

This is normally done by taking the system through a specific set of trajectories which allows the system to identify and compensate for the associated misalignment angles and levers arms.

The calibration process is however affected by many factors including environment, vehicle dynamics, GPS accuracy, etc. and it can therefore be difficult to achieve reproducible calibrations result and thereby accuracy.

All our hybrid navigators, i.e. SPRINT-Nav and SPRINT-Nav Mini, goes through a factory calibration at our test facility in Plymouth. This factory calibration is achieved in the same environment, using the same vehicle and GPS receiver meaning we will achieve the highest possible accuracy throughout every calibration.

For our users this means you get the highest possible performance straight out of the box without having to through a complex calibration process.

Further, all our hybrid navigators ship with a performance certificate showing exactly how it performed during the calibration process.

Contact [email protected] for more information.

How does installation position affect ROVNav 6+?

The ROVNav 6+ transceiver relies on line of sight to other transducers or transceivers in order to send and receive signals. If the transceiver is positioned to close to or within a Remotely Operated Vehicle (ROV), it is likely that there will be some signal blocking in one or more directions. Therefore, it is advised to have the ROVNav 6+ transceiver positioned in a clear unobstructed area to provide the best performance.

Here are a few points to consider when installing your ROV Nav 6+ Transceiver:

• Typically, transceivers are installed at the top of a vehicle, this will provide 360 degree visibility
• Install your transceiver away from any thrusters to prevent thruster wash which can interfere with signals as it introduces noise
• If possible, install transceivers on an extendable arm, which can increase the height of the transceiver when in use. Keep it protected if vehicle is in a Tether Management System or garage and ensure you have enough slack in the cable, so it does not get trapped when extended