Operational checks on X and S band radar by radio surveyor

Shipaxis Technical Services


8.4) Operational checks to be carried out by Radio Surveyors in Radar Equipment during Survey
8.4.1) Surveyors should check the overall performance of the radar installation by careful observation of known echo responses in the vicinity of the ship. This is a subjective method and relies on the judgement of the surveyor with experienced appreciation of the quality of a radar picture which can be obtained in the area.
8.4.2) The operation of Performance Monitors should also be checked and, where possible, the monitor responses should be compared with the calibration label or record.
8.4.3) The alignment of the radar heading-marker with the ship's fore-and-aft line should be checked by comparing visual bearings, relative to the ship's head, of identified radar echoes with the bearings on the display between the echoes and the heading line. The visual bearings should, where practicable, be taken from positions which do not introduce parallax into the alignment procedure. Where inter-switching facilities are provided the Surveyor should ensure that the indicated heading marker is accurately aligned with all arrangements of units. Where the heading marker is not accurately aligned, the Master should be informed and be requested to carry out a re-alignment before the ship sails.
8.4.4) Where electronic plotting aids are provided with test programmes or facilities to enable the integrity of the equipment to be checked, as described in the Operating Manual, Surveyors should make use of these test programmes or facilities when assessing the performance of the radar installation.
8.5) Measurement of Shadow Sectors
8.5.1) Calculation from a knowledge of the width of a mast or other object which might cause a shadow, and its bearing from the centre of the radar antenna, can provide a useful guide to the possible appearance of shadow sectors on a radar display. However, the actual angular width and bearing on any shadow sectors should be determined at sea. Two possible methods are: 
a) Observations of the behaviour of the echo of a small isolated object, such as a buoy not fitted with a corner reflector or a beacon post, when the ship is turned slowly through 360° at a distance of a mile or so from the object. The display unit should be carefully watched, and the bearings between which the echo from the buoy disappears and re-appears taken as indicating the shadow sector or sectors. The sea should be calm so that the echo is not lost in the sea clutter or submerged or hidden by waves from time to time, or in the case of a buoy or other floating objects the echo fading temporarily due to any rolling motion.

b) Observation of the shadow secto r against a background of sea clutter.

Note:

A shadow sector cannot be fairly estimated in heavy clutter, as echoes from either side of the sector may spread into it and give an illusion that objects in the sector are being observed. Nor can it be satisfactorily determined in confined water, because of the probability of indirect, false or multiple echoes being produced from nearby buildings or other ships.
8.6) Radar plotting facilities
8.6.1) SOLAS V/19 specifies carriage of three types of radar plotting aid. The type carried depends upon the size of the ship. Each plotting aid forms an integral part of the radar unit. Surveyors should check that accurate heading and speed information is input to the equipment and that the speed is measured through the water in the fore and aft direction. Surveyors should check that GPS is not being used to provide speed information for ARPA and ATA. GPS provides speed over the ground and the ARPA/ATA display will be misleading in sea areas that experience significant tidal steams and currents if used for collision avoidance.

All plotting aids must provide target information which must include plot number, range and bearing, CPA and TCPA, and true course and speed. 

ANNEX 16 - Radar Equipment explains the difference in capabilities between each type.

8.6.1.1) Electronic Plotting Aid (EPA)
8.6.1.2) Surveyors should, if possible, check that at least 10 targets can be manually plotted with selectable true and relative vectors on at least the 3,6 and 12 nm. range scales.
8.6.2) Automatic Tracking Aid (ATA)
8.6.2.1) Surveyors should check, if possible, that at least 10 targets can be acquired and automatically tracked with selectable true and relative vectors on at least the 3,6 and 12 nm. range scales.
8.6.2.2) Auto-tracking must be able to trigger an alarm when a target transits a selected zone or range, CPA, TCPA and when a target is lost.
8.6.3) Automatic Radar Plotting Aid (ARPA)
8.6.3.1) Surveyors should check, if possible, that at least 20 targets can be acquired both manually and automatically.
8.6.3.2) ARPA must be able to be sea or ground stabilised.
8.6.3.3) ARPA must be able to trigger an alarm when a target transits a selected zone or range, CPA, TCPA and when a target is lost.
8.6.3.4) A trial manoeuvre facility must be provided to assess the effect of any proposed manoeuvre of own-ship.
8.6.3.5) The ARPA should be provided with test programmes to enable the integrity of the equipment to be checked. These are described in the Operating Manual. Surveyors should make use of these test programmes or facilities when assessing the performance of an ARPA

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