Transmitting Heading Device
| Back to: | CIRM Knowledge Base |
| Page completeness level: | High |
Contents
Overview
A Transmitting heading device (THD) is an electronic device that provides information about the ship’s true heading. Can be magnetic, gyroscopic (i.e. Gyrocompass), or GNSS (e.g. Satellite compass).It provides heading information to the radar, plotting aid, and AIS.
Performance standards, testing standards and carriage requirements
Performance standards
MSC.116(73) contains the Performance Standards for Marine Transmitting Heading Devices (THDs), covering THDs of the magnetic, GNSS or gyroscopic types.
Testing standards
- ISO 22090-2 (Magnetic)
- ISO 22090-1 (Gyroscopic)
- ISO 22090-2 (GNSS)
Carriage requirements
(Solas Chapter V Reg. 19) All ships of 300 gross tonnage and upwards and passenger ships irrespective of size shall, in addition to meeting the requirements of paragraph 2.2, be fitted with a properly adjusted transmitting heading device, or other means to transmit heading information for input to the equipment referred to in paragraphs 2.3.2, 2.3.3 and 2.4.
Detailed requirements
MSC.116(73)
| Defintions | ||
|---|---|---|
| Heading | for the purpose of these standards any ship’s heading to be input to the THD function | |
| Sensing part | a sensing function of detecting any heading information connected to the transmitting device | |
| Transmitting part | device which receives a heading information from the sensing part and convert to the required accurate signal | |
| True heading | horizontal angle between the vertical plane passing through the true meridian and the vertical plane passing a through the craft’s fore and aft datum line. It is measured from true north (000) clockwise through 360 degrees | |
| Transmission and resolution error | error which is caused by the method used to transmit the original information to a receiving device. Such method may have a limited capability to code any possible value of the information e.g. step output with 1/6 deg. resolution. This error is caused by the method used inside the THD and at its output to code the information | |
| Static error | error which is caused by any reason and which stays unchanged in value during the operation of the system. This error should be measured under static condition | |
| Dynamic error | error which is caused by dynamic influences acting on the system such as vibration, roll, pitch or linear acceleration. This error may have an amplitude and usually a frequency related to the environmental influences and the parameters of the system itself | |
| Follow-up error | error which is caused by the delay between the existence of a value to be sensed and the availability of the corresponding signal or data stream at the output of the system. This error is e.g. the difference between the real heading of turning vessel and the available information at the output of the system. The follow-up error disappears when the system is static | |
| Operational requirement | ||
| 4.1 Functionality | 4.1.1 | The THD receives a heading signal and generates a suitable output signal for other devices |
| 4.1.2 | Any sensor part may be included in the device | |
| 4.1.3 | Any correcting devices or parameters should be protected against inadvertent operation | |
| 4.2 Presentation of information | 4.2.1 | All displays with the exception of the sensor, and all outputs of heading should indicate true heading |
| 4.2.2 | Manually settable values used for electronic correction should be indicatable by adequate means | |
| 4.3 Accuracy | 4.3.1 | The THD should be tested for accuracy with the sensing part connected. If the sensing part is so designed that it is included in the transmitting part, the equipment should be tested together with all parts |
| 4.3.2 | The THD should meet at least the following accuracy at the output of the device under sea conditions as specified in resolution A.424(XI) or A.821(19) as applicable: .1 Transmission and resolution errors. The transmission error including the resolution error should be less than ±0.2º; | |
| 4.4 Interfacing | 4.4 | At least one output should be in accordance with the relevant international marine interface standard |
| 5 Electromagnetic compatibility | 5 | The device, with regard to electromagnetic interference and immunity, should, in addition to resolution A.694(17), comply with resolution A.813(19). |
| 6 Failure conditions | 6 | An alarm should be provided to indicate malfunctions of the THD or a failure of the power supply. |
