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 non-visual aids are employed. The organization to achieve this is called the blind pilotage organization, comprising a BP team, led by a BP Officer (BPO).
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 a 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 ships lateral position relative to the planned track. On the chart (Fig. 1), a line is drawn from the edge of a radar-conspicuous object, parallel to the
The perpendicular distance (or cross-index range) from the object to the track is then measured. The range strobe on the radar is then set to this range, and a solid chinagraph line drawn on the display parallel to the planned course on a scale appropriate to the range in use.
Positions 1, 2, and 3 on the chart and radar display show the ship on track at various instances up to the 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 the nearest point of Radar clearing ranges (Fig. 2) are similarly drawn at the maximum or minimum distances from the radar conspicuous objects to keep the ship clear of dangers.
These are drawn as broken lines:_ _ _ _ _ _ _ _ _.
What is Blind Pilotage?
Navigating the vessel in restricted visibility
The principle of non-visual aid to navigation is the ship’s radar.
Other non-visual aids are also employed e.g. AIS, echo sounder, ROTI.
Factors to consider
The degree of risk involved in restricted waters must be carefully assessed prior to entering. Bridge watches may be doubled up & watch level upgraded.
Congestion due to other shipping should be considered. Both radars / ARPA should be operational.
Consequences of failure of radar or other vital aids should be considered & risk assessment should be done.
The availability of navigational aids, which can be used in restricted visibility, must be taken into account. Racons, AIS buoys/stations, VTS, etc.
Parallel indexing can be used as a powerful tool for position monitoring & execution of passage.
Draw one set of parallel index lines ahead of those in use.
Plan the passage so as to Steer a course to pass a given distance off a radar conspicuous point, Alter course off a navigational mark or point of land.