Output telegrams are used to transmit beacon or mobile vehicle position information from Ranger 2 to external systems such as a dynamic positioning (DP) desk or navigation package.
Several industry-standard telegram formats are supported, including HPR 309, HPR 418 BCD and HPR 418 F. These formats are widely used on DP vessels for the transfer of hydro-acoustic position reference (HPR) data between acoustic positioning systems and third-party equipment.
Whilst Ranger 2 calculates and displays acoustic positioning information internally, external systems cannot directly interpret this data. Output telegrams provide a standardised interface that packages position, quality and status information into a format that can be understood by the receiving system.
Correct configuration of the output telegram is essential to ensure that positional data is transmitted accurately and that the DP system interprets the information as intended. This article explains the purpose of DP output telegrams and the key configuration parameters available within Ranger 2.
Selecting a telegram type
Ranger 2 supports a variety of output telegram formats, including HPR, SSB, LBP, as well as Sonardyne proprietary telegrams.
The required telegram type is determined by the receiving DP or navigation system and should always be specified by the DP system manufacturer. As there is no universal standard across all vessels and third-party systems, Sonardyne cannot determine the correct telegram format without this information.
If there is any uncertainty regarding the required telegram format, the customer should consult the vessel documentation or contact the DP system manufacturer before configuration proceeds.
Common examples of DP output telegram include:
- HPR 309
- HPR 418
- HPR 418 BCD
- SSB
- LBP
- PSONDP
Telegram index
Each telegram is assigned a numerical index which is used by the receiving system to identify the associated beacon, vehicle or positioning source.
It is important that the index configured within Ranger 2 matches the value expected by the receiving system. An incorrect index may result in the position data being ignored or assigned to the wrong target.
For example, a beacon configured with an index value of 107 may be displayed by the receiving system as B07, which is commonly seen for HPR telegrams.
Frame of reference
The reference frame determines the coordinate origin used for the reported position.
Available options include:
- DP reference waypoint
- Ship
- Subsea vehicle
- Structure
- World (where supported by the selected telegram)
Note: When using a world reference frame, a valid GPS/GNSS input is required as the position will be reported in geographical coordinates.
The selected reference frame should match the operational requirement and the expectations of the receiving system.
For example:
- Ship frame reports position relative to the vessel.
- DP reference waypoint reports position relative to the selected DP reference location.
- World frame reports position in a geographical coordinate system.
An incorrect reference frame may result in unexpected positional offsets being observed at the DP desk.
Orientation
The orientation setting determines how the position coordinates are presented.
North up – Coordinates are referenced to true North.
Bow up – Coordinates are referenced to the vessel heading.
This setting must match the coordinate convention expected by the receiving system. If an incorrect orientation is selected, position data may appear rotated or mirrored when displayed externally.
Source selection
The source setting determines which positioning solution is used to generate the output telegram.
Filtered
Filtered is the default setting and is recommended for most DP applications.
A Kalman filter is applied to the acoustic positioning solution to reject outliers and provide a stable position output. This generally results in smoother and more reliable position information being supplied to the DP system.
Raw
Raw uses a least-squares position estimate without filtering.
As velocity is not estimated, the reported position is not compensated for vessel movement during acoustic signal travel time. Whilst this can provide a more immediate solution, it can also result in noisier position data and increased position scatter.
INS
INS outputs the DP-INS solution and is available for the vessel only.
SPRINT
SPRINT outputs a position solution referenced to the time of interrogation rather than the time the acoustic reply is received. This option is intended for applications utilising SPRINT inertial technology.
For the majority of DP applications, Sonardyne recommends using filtered output unless a specific operational requirement dictates otherwise.
Additional DP parameters
The following parameters can be amended in the ‘Report Properties’ under the ‘Advanced’ tab. Any deviation from the default settings should be understood and justified by the operational requirements.
Spacing
Defines the minimum time interval between consecutive telegram transmissions. The default value is zero.
For HPR418D and HPR418F binary telegrams, the specified gap is 40 ms.
Maximum repeat count
Limits the number of times a telegram may be retransmitted. The default value is zero (disabled).
SD limit
Prevents telegram output if the predicted error exceeds a specified threshold. This can be useful when preventing low-confidence positional data from being supplied to the DP system.
Error scale factor
The error scale factor adjusts the reported error ellipse radius. The valid range is 0.1 to 10, with a default value of 1.0.
Adjusting this value will alter the quality information presented to the receiving DP system and should only be modified where specifically required by vessel procedures or DP manufacturer guidance.
Invert pitch / invert roll
Allows the sign convention of pitch and roll values to be reversed where required by third-party systems.
Common configuration pitfalls
The following configuration issues are commonly encountered during vessel commissioning and troubleshooting:
- Incorrect telegram index configured.
- Reference frame does not match the receiving system configuration.
- Orientation set to North up when bow up is expected (or vice versa).
- Raw output selected when filtered output is required.
- Error scale factor modified from its default value without justification.
- Incorrect telegram type selected for the receiving system.
When troubleshooting DP position issues, these settings should be verified before investigating more complex system faults.
Further reading
For additional information, please refer to:
Ranger 2 User Manual – Section 4.23: Configuring Output Telegrams.
Ranger 2 User Manual – Appendix E: Output Telegram Formats.
Ranger 2 User Manual – Appendix J: Frames of Reference.
If you have any issues, contact [email protected]