KONGSBERG HiPAP System Operation and Maintenance Guide

KONGSBERG HiPAP Underwater Acoustic Positioning System: Complete Manual for Selection, Configuration, and On site Troubleshooting

Accurate underwater positioning is the cornerstone for ensuring safety and efficiency in deep-sea exploration, dynamic positioning drilling, underwater robot (ROV) navigation, and subsea pipeline laying operations. The ultra short baseline (SSBL/USBL) system has become the mainstream in the industry due to its simplicity of only requiring a single transducer on board and an underwater responder. However, the bending of sound rays, multipath interference, changes in ship posture, and noise pollution in deep water environments can all lead to a sharp amplification of positioning errors.

Kongsberg Maritime's HiPAP (High Precision Acoustic Positioning) series is globally recognized as the benchmark for high-performance underwater positioning. From the flagship model HiPAP 501 (241 element spherical transducer) to the portable HiPAP 351P, and then to the ultra deep water HiPAP 101 (working depth of 6500 meters), this family covers various application scenarios from shallow water to full sea depth. This article is based on the technical specifications of the HiPAP system, combined with practical engineering experience, to systematically explain the installation specifications of transducers and deck units, the configuration of APOS operating system, the selection principles of SSBL/LBL positioning modes, the advantages of Cymbal broadband protocol, and the most commonly encountered fault diagnosis and troubleshooting methods on site. Whether you are a DP operator, acoustic positioning engineer, or ROV navigator, this article will be an essential technical reference for you to carry with you.

HiPAP System Architecture and Core Technologies

2.1 System Composition Modules

A complete HiPAP system includes the following core components:

Transformer: Installed at the bottom of a ship or a telescopic hull unit, it is responsible for transmitting acoustic interrogation signals and receiving replies from responders. The number of array elements varies from tens to 241 depending on the model.

Transceiver Unit: Installed near the hull unit, it contains a digital transmitter, preamplifier, and beamforming electronic components, and communicates with the operation station through optical fibers.

Operator Unit: An industrial computer running APOS (Acoustic Positioning Operating System) software, equipped with a color display, keyboard, and trackball. Support multiple workstations, one primary and multiple backup.

Hull Unit: A lifting mechanism with gate valves that can extend the transducer several meters out of the bottom of the ship, avoiding the bubble layer near the waterline and propeller disturbance of the water flow. Ensure safe use within a speed of 10 knots.

Transponder/responder: Installed on underwater targets. The traditional MPT/SPT series uses FSK modulation, while the new cNNE series supports Cymbal broadband protocol and over 100 channels.

2.2 Beamforming principle of transducer

The core difference between HiPAP and ordinary USBL systems is full digital beamforming. Each transducer element is independently connected to the DSP, which measures the phase and amplitude of the incident signal to accurately calculate the horizontal and vertical angles of the responder. All models adopt automatic focusing narrow transmission/reception beam technology, and the beam direction is dynamically directed towards the target responder by the tracking algorithm. The advantages brought by narrow beam:

The signal-to-noise ratio (S/N) has significantly improved, enhancing the accuracy of angle measurement and maximum operating range.

Suppress acoustic reflections (multipath interference) and environmental noise from other directions.

For HiPAP 501, the receiving beamwidth is only 10 °, achieving an angle measurement accuracy of 0.03 ° level.

2.3 Cymbal Protocol - Broadband Direct Sequence Spread Spectrum

The second generation HiPAP 501/451/351/101 introduced the Cymbal acoustic protocol and adopted direct sequence spread spectrum (DSSS) technology. Compared to traditional narrowband CW pulses, Cymbal has the following revolutionary improvements:

Angle accuracy improved by 30% (in SSBL mode)

The ranging accuracy reaches 0.02 meters (up to 0.01 meters between cNNE responders)

Significant increase in operating distance

Enhanced multi-path suppression capability

Support Multiplaying to improve location update rate

Automatically adjust the transmission power of the responder to extend battery life

High speed telemetry data rate (up to 8 kbit/s), interleaved transmission of data and positioning signals

Add 50 independent responder channels (based on the original 56 channels)

No mode switching: The responder can dynamically switch between SSBL and LBL

Installation and Integration Specification

3.1 Installation points of transducers and ship units

Installation location: Keep as far away as possible from the bow thruster, side thruster, propeller, and bilge drain. It is best to install telescopic hull units through moonpools or flat areas in the middle of the hull.

Sinking depth: During operation, lower the transducer to at least 2 meters below the bottom of the ship, but avoid the risk of bottoming out. Shallow water operations can partially retract.

Gate valve maintenance: The hull unit is equipped with manual or hydraulic gate valves, which can replace the transducer without entering the dock. Check the seals and lubrication once a year.

Cable path: The transducer cable (multi-core shielded) to the transceiver unit should be avoided from being laid parallel to high-power cables (such as frequency converter output), with a minimum spacing of 0.5 meters.

3.2 External Sensor Interface

HiPAP must be connected to the following external sensors to achieve nominal accuracy:

Sensor type affects recommended devices

The heading directly affects the horizontal azimuth angle, and the error increases with the horizontal offset of the fiber optic compass (accuracy<0.1 °)

Motion Reference Unit (MRU) compensates for ship roll/pitch, and the accuracy directly affects the final positioning error. Kongsberg MRU 5 (accuracy 0.03 °)

Sound velocity profiler (SVP) calibrates sound ray bending (refraction) errors using a projection or CTD probe, in real-time or input profile files

GNSS (GPS/DGPS) converts underwater coordinates to absolute geographic coordinate differential GPS with an update rate of ≥ 1Hz

The Golden Rule: Do not use low precision MRUs with HiPAP systems. The total position error is the sum of HiPAP's own error and sensor error. Spending tens of thousands of dollars to purchase HiPAP with a cheap attitude sensor is not worth the loss.

3.3 Networked deployment of APOS operating system

APOS runs in a Windows environment and supports multiple operating stations. Configuration points:

Main station: Connect the fiber optic transceiver unit to control all functions.

Slave station: communicates with the master station through Ethernet, can view data in real time, and can take over the master control at any time (with no quantity limit).

Data output: Output standard NMEA or proprietary statements (such as $PSXN, 20) to DP systems and survey software (such as EIVA, QINSy) through serial ports (RS-232/422) or UDP Ethernet.

Deep analysis of SSBL and LBL positioning modes

4.1 SSBL (Ultra Short Baseline) Mode

Principle: The shipborne transducer measures the horizontal angle, vertical angle, and slant distance of the responder, and calculates the relative position through trigonometric geometry. Due to the linear amplification of angle error with distance, the accuracy of SSBL is inversely proportional to the operating distance.

Applicable scenarios:

Within a water depth of 500 meters, rapid deployment is required without laying an underwater array.

Track a single moving target (such as ROV, towed fish).

Acoustic reference for dynamic positioning (DP) system.

Optimization techniques:

The use of a narrow beam (HiPAP 501's 10 ° beam) can significantly suppress angle errors.

Enable Cymbal protocol to achieve a 30% accuracy improvement.

Real time input of sound velocity profile and correction of sound line curvature.

4.2 LBL (Long Baseline) Mode

Principle: Set up an array of three or more responders on the seabed, and calculate the position of the ship relative to the array by measuring the slant distance between the ship and each responder. The accuracy of LBL is almost independent of water depth, and only depends on the geometric accuracy of the formation and ranging error.

Applicable scenarios:

High precision positioning requirements for deep water (>1000 meters).

Installation of underwater structures (such as templates, Christmas trees, BOP).

Multi User Localization (MULBL): Multiple ships or ROVs share the same underwater array.

HiPAP's LBL features include:

Fast LBL responder positioning: Automatically measure all baseline distances within the array.

Accurate measurement mode: used for precise measurement before installation of underwater facilities, with a relative accuracy of centimeter level.

Geographical LBL calibration: Use GPS to calibrate the absolute coordinates of the underwater array.

4.3 Mixed use strategy

In actual deepwater operations, a combination of "LBL array for ship positioning+SSBL for ROV positioning" is often used. HiPAP allows for no mode switching of the responder, and the same cSIDE responder can simultaneously respond to LBL ranging and SSBL interrogation, greatly improving operational efficiency.

Key points of APOS operation and configuration

5.1 Initial Setup Wizard

After the first use or reinstallation, the following calibration must be performed:

Automatic transducer alignment calibration: Select a known position water surface responder (such as hanging on the side of the ship), and automatically calculate the installation angle (yaw, pitch, roll) of the transducer relative to the ship reference point through the APOS menu "Calibration ->Transformer Alignment". This process needs to be carried out under calm sea conditions.

Sound Velocity Profile Input: On the "Sound Velocity" page, you can manually input the depth sound velocity table or receive CTD profile data in real-time through the serial port. The system will correct the curvature of the radiation in real-time based on this.

Sensor offset: Input GNSS antenna MRU、 The lever arm of the electric compass relative to the reference point of the ship. APOS will be uniformly converted to the ship coordinate system.

5.2 Deployment and activation of responders

When using cSIDE responder:

Activate the dormant responder by sending the "Wake Up" command through HiPAP.

Assign unique channel numbers (1-106, including 56 traditional channels and 50 Cymbal extension channels).

Set the transmission power level of the responder, balancing battery life and maximum operating distance.

For LBL arrays, use the "LBL Translator Positioning" function to automatically measure the baseline and establish the array.

5.3 Data Display and Output

APOS graphical interface provides:

Horizontal position diagram (top view of the ship relative to the transponder or array)

Depth profile (vertical section)

Historical trajectory (adjustable storage interval)

Digital data display (coordinates, distance, angle, signal-to-noise ratio, etc.)

When transmitting data to the DP system, the following options can be selected:

Raw location data (output per ping)

Smooth position after Kalman filtering (recommended for DP)

Common troubleshooting and on-site diagnosis

6.1 Fault 1: Unable to receive responder signal ("No Reply")

Phenomenon: APOS shows that the interrogation has been transmitted, but there is no effective echo from the responder.

Possible reasons:

The responder is not turned on or the battery is depleted.

The channel number does not match.

The transducer is blocked (covered by bubbles, marine organisms, or sediment).

Sound bending causes the beam to not point towards the responder.

The responder has exceeded its maximum operating distance.

Solution steps:

Check if the responder is in the "Active" state in the APOS "Translator Status". If not, try sending a forced wake-up command.

Confirm that the responder channel number is consistent with the APOS settings (including Cymbal and traditional mode).

Check the surface of the transducer: If the hull unit has been raised, visually inspect for any attachments. Diving for cleaning if necessary.

Check the noise spectrum analyzer (APOS built-in function): if the ambient noise in the frequency band is too high (such as nearby construction, ship propeller cavitation), try to reduce the speed or move the operation area.

Input the accurate sound velocity profile and observe whether the beam deviates beyond the mechanical inclination range of the transducer due to refraction.

Gradually increase the transmission power of the responder (be careful not to exceed the maximum rated value).

6.2 Fault 2: Positioning jump or abnormal dispersion (poor accuracy)

Phenomenon: The position display of the responder is unstable, jumping several meters in a short period of time.

Possible reasons:

MRU data loss or low accuracy.

Electric compass data interruption or delay.

Multipath interference (from ship bottom, water surface reflection, or steep seabed slopes).

The installation angle calibration of the transducer is inaccurate.

Solution steps:

Check the "Sensor Input" page of APOS to see if the Heading, Roll, and Pitch are updated at ≥ 10Hz. If the value is stationary, check the serial communication or the sensor itself.

Turn on 'Ray Tracing Display' in the graphic view and observe if there are any noticeable peaks in the reflected waves. If there are multiple paths, you can try disabling automatic gain control and manually setting a lower gain to ignore reflected waves.

Re execute automatic transducer alignment calibration. If mechanical deviation is suspected, it can be verified using a water surface responder at a known location.

Enforce the use of Cymbal protocol (if available), which has stronger multipath suppression capability in its spread spectrum encoding.

For LBL mode, check if the baseline measurement of the array is correct and if there is any responder position drift.

6.3 Fault 3: Failure of heave compensation or incorrect display of water depth

Phenomenon: The depth value of the responder deviates significantly from the actual deployment depth, or it shakes violently with the ship's rise and fall.

Possible reasons:

The depth sensor of the responder is not calibrated or faulty.

APOS is not connected to the correct sound velocity value.

The vertical reference of MRU is incorrect.

Solution steps:

Compare the depth displayed by APOS with the actual deployment depth of the responder (such as the winch counter). If the error exceeds the theoretical value of "sound velocity error x slant distance", first check the sound velocity profile.

If the responder has a built-in pressure sensor, the raw pressure value can be read and the zero point calibrated through APOS' Read External Sensor '.

Confirm whether the Heave data output by MRU is reasonable: it can be compared with the shipborne wave meter on a still water surface. If the MRU experiences drift, refer to the calibration steps for MRU 5 mentioned earlier.

6.4 Fault 4: Communication interruption between APOS and transceiver unit ("Transceiver Lost")

Phenomenon: Communication error displayed on the operation station, unable to control transmission or reception.

Possible reasons:

Fiber optic breakage or connector contamination.

The power supply of the receiving and transmitting unit is faulty.

The internal board of the transceiver unit is overheating.

Solution steps:

Check the indicator light on the receiving and transmitting unit panel: The PWR (power supply) should be constantly on; The status should flash. If it doesn't light up, measure the input voltage (24VDC or 110/230VAC depending on the model).

Test the attenuation of fiber optic links using an optical power meter. If the loss is greater than 15dB, clean the connector end face (with a dedicated cleaning tape) or replace the optical cable.

If the transceiver unit overheats (such as poor ventilation in the cabinet), suspend operation and force cooling to check if the fan is running.

Spare parts suggestion: Keep a fiber optic jumper between the transceiver unit and APOS, as well as a transceiver unit power module.

6.5 Fault 5: DP system unable to lock HiPAP position

Phenomenon: The HiPAP reference value on the DP console fluctuates too much, causing DP to frequently refuse to use.

Possible reasons:

The filter parameters of the DP system do not match the HiPAP update rate.

The language or verification method of the data output by HiPAP is incorrect.

External sensor time delay not compensated.

Solution steps:

Check if the communication protocol of HiPAP is set to "Raw data" (recommended) in the DP system. DP should perform its own Kalman filtering instead of using the internally smoothed data from HiPAP.

Confirm that the output rate of HiPAP is consistent with the expected DP (usually 1-2Hz).

If using NMEA format, check for checksum errors. APOS can output standard NMEA statements with verification.

Measure the total delay (usually 0.5-2 seconds) from acoustic signal emission to DP data reception, and set the corresponding delay compensation in the DP system.

Dual HiPAP system and HAIN integrated navigation

7.1 Dual transducer configuration

On DP3 class vessels or drilling platforms that require extremely high reliability, two independent HiPAP transducers (such as port and starboard) can be installed. Advantage:

Electrical redundancy: One set fails and the other seamlessly connects.

Acoustic redundancy: One of the transducers may be located in quieter waters or avoid reflectors.

Accuracy improvement: By using specialized software to statistically fuse the positions of two independent systems, SSBL accuracy can be improved by a factor of one/two1/ two.

7.2 HAIN (Underwater Acoustic Assisted Inertial Navigation)

HAIN combines the absolute drift free position of HiPAP with the high-frequency and low-noise characteristics of the inertial navigation system (IMU). Especially valuable for ROV and deepwater operations:

Improve position update rate: Between two acoustic positioning operations, the IMU calculates the position and outputs a smooth trajectory.

Extend the battery life of the responder: It can reduce the acoustic positioning frequency to once every 10-30 seconds, while still maintaining stable display through IMU.

Availability during acoustic interruption: When the signal is obstructed by obstacles or encounters strong noise, HAIN continues to provide position with drift much smaller than pure inertial navigation.

Deep water accuracy improvement: After the water depth exceeds 3000 meters, the acoustic positioning update rate decreases to once every few seconds, filling the gap with HAIN.

All HiPAP systems can be integrated with HAIN and are divided into:

HAIN Subsea: Inertial module installed on ROV.

HAIN Reference: A reference system installed on a vessel or platform.

Model selection suggestions and upgrade path

Model: transducer structure, beamwidth, maximum working depth, typical application can be upgraded to

HiPAP 501 spherical, 241 elements with top precision of 10 ° 4000 m, omnidirectional coverage-

HiPAP 451, similar to the 501 sphere, only activates the bottom 46 elements with a 15 ° 3000 m medium precision, and can be fully upgraded to HiPAP 501

HiPAP 351 spherical bottom 46 elements 15 ° 3000 m economical, compatible with old 355mm gate valve, non upgradable

HiPAP 351P portable, equipped with MRU and compass 15 ° 2000 m for temporary installation and chartering operations-

HiPAP 101 low-frequency, mechanical tilting directional 6500 m ultra deep water, ROV tracking-

Upgrade suggestion: Purchase HiPAP 451 instead of directly purchasing 351, as the former can be upgraded to 501 performance through software and adding a transceiver board, protecting investment.

Regular maintenance and daily inspections

9.1 Monthly maintenance items

Check the lifting function of the hull unit, lubricate the screws and seals.

Play back the 'System Log' in APOS to check for frequent communication errors or responder lockout records.

Perform noise spectrum analysis: Record the noise level of typical frequency bands, compare it with historical data, and determine whether there are new interference sources (such as frequency converter harmonics).

9.2 Maintenance every six months/year

Raise the transducer and clean the surface (use a soft bristled brush and fresh water, do not direct high-pressure water gun directly onto the ceramic surface).

Check for capacitor bulges and connector oxidation on the internal boards of the transceiver unit.

Verify the overall accuracy of the system through a known responder (such as a reference responder suspended at a depth of 1 meter on the ship's side): compare the distance calculated by APOS with the actual physical distance, and the error should be within<0.2% (for example, the error at 100 meters should be<0.2 meters).

9.3 Spare Parts List (Recommended)

One complete cNose responder (depth level matched with the work area)

Transmission and reception unit power module

Sealing kit for ship unit gate valve

Multi core cable between transducer and transceiver unit (5-meter spare section)

Fiber optic jumper (ST or SMA connector, 2 pieces)