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ABSTRACT
Blind pilotage means the navigation of the ship through restricted waters in low visibility with little or no recourse to the visual observation of objects outside the ship. The principal non-visual aid to navigation that enables this to be done is high-definition warning-surface radar, but all available nonvisual aids are employed. The organisation to achieve this is called the blind pilotage organisation, comprising a BP team, led by a BP Officer (BPO).
Keywords: blind pilotage, blind anchorage.
1. INTRODUCTION
Assessment of the risk involved in a blind pilotage passage
Although normally the accuracy of blind pilotage is such that a ship can be taken to an open anchorage and anchored within 50 yards of the desired place, the degree of risk involved, particularly in restricted waters, must be carefully assessed. Congestion due to other shipping, the consequences of failure of radar or other vital aids once the ship has been committed to her passage, and the number and quality of fixing marks must be taken into account.
Parallel index technique
The key to blind pilotage is the principle of the parallel index. The running of a parallel index line provides real-time information on the ship's lateral position relative to the planned track. On die chart (Fig. 1), a line is drawn from the edge of a radar-conspicuous object, parallel to die planned track.
The perpendicular distance (or cross-index range) from the object to the track is then measured. The range strobe on the radar is tiien set to this range, and a solid chinagraph line drawn on die display parallel to the planned course on a scale appropriate to die range in use. Positions 1 , 2 and 3 on die chart and radar display show die ship on track at various instances up to die time that the island is abeam to starboard.
Positions 4 and 5 show the ship off track to port. The exact distance off track can be measured by dividers from the radar echo of the island to die nearest point of the chinagraphed parallel index line at the scale of the display. This can be made easier by constructing scales for each range setting, as shown below, and mounting them adjacent to die display. (The crosses on...