Navigating in Poor Visibility

1. Grunt Productions 2007
BLIND PILOTAGE
A Brief By Lance Grindley

2. Definition:
‘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.’

3. Grunt Productions 2007
BLIND PILOTAGE
1. Navigation and Pilotage
a) Primary method: Visual
b) Secondary method: Radar
c) Other methods: ‘NAVAIDS’
2. Fundamental Navigational Radar
a) Stabilised in azimuth
b) Bearing accuracy ±1°
c) Range accuracy better than 20 yds (depending on pulse
length)
d) Anti-clutter controls
e) Range scales (1007)
0.5, 0.75, 1.5, 3, 6, 12, 24, 48 miles
f) Fitted with: Electronic Blind Pilotage System

4. Grunt Productions 2007
PLANNING
 TRACK - Chosen by Master, based on
visual plan.
 SAFE WATER - Delimited by Limiting
Danger Line (LDL):
Draught+2m-Height of Tide.

5. Grunt Productions 2007
BLIND PILOTAGE
• Where are we in relation to planned
track ?
• How much safe water remains ?
• How far to run to the next course
alteration ?

6. Grunt Productions 2007
Parallel Indices
2m

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WO
7.6c
4.0c
5.2c

8. Grunt Productions 2007

9. Grunt Productions 2007
WO
7.6c
4.0c
5.2c
NMT 11c
NLT 2c
NMT 13c
NLT 1c

10. Grunt Productions 2007

11. Grunt Productions 2007
WO
7.6c
4.0c
5.2c
NMT 11c
NLT 2c
NMT 13c
NLT 1c
6.2c

12. Grunt Productions 2007

13. Grunt Productions 2007

14. Grunt Productions 2007

15. Grunt Productions 2007
270 (270)
1m
NLT 4c
NLT
5c
1.3m
1.4m

16. Grunt Productions 2007
IN POSITION

17. Grunt Productions 2007
Radar Errors
 Index Errors

18. Grunt Productions 2007
Ie +/- 50 yds

19. Grunt Productions 2007
FINDING THE INDEX ERROR
TWO MARK METHOD
A = True range ± IE
B = True range ± IE
C = Charted distance
Index error = C – (A + B)
2
A B
C
Index error

20. Grunt Productions 2007
Three Mark Method

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False Echo

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Two Ship Method
Compare B to A to find Index Error. IE = B - A = C - 2A
A(IE)
Range (A) between own ship and other incorporates Index Error.
C (IE)
Range (C) between own ship and false echo also incorporates Index Error.
B(No IE)
True Range is therefore C-A which equals B.

23. Grunt Productions 2007
Radar Errors
 Index Errors
 Strobe Accuracy

24. Grunt Productions 2007
Distortion caused by beam width
Direction of
Aerial Rotation
A2
A1
B
C
D
Coastline
E

25. Grunt Productions 2007
Radar Errors
 Index Errors
 Strobe Accuracy
 Error introduced by controls

26. Grunt Productions 2007

27. Grunt Productions 2007
Radar Errors
 Index Errors
 Strobe Accuracy
 Error introduced by controls
 Inaccuracies by not using shortest
range scale

28. Grunt Productions 2007
Radar Errors
 Index Errors
 Strobe Accuracy
 Error introduced by controls
 Inaccuracies by not using shortest
range scale
 Sloping beach/HOT

29. Grunt Productions 2007

30. Grunt Productions 2007

31. Grunt Productions 2007
Radar Errors
 Index Errors
 Strobe Accuracy
 Error introduced by controls
 Inaccuracies by not using shortest
range scale
 Sloping beach/HOT

32. Grunt Productions 2007
EXECUTION
 Ensure chart and PI’s are accurate.
 Conduct time check.
 Maintain constant commentary -
“30 yds port of track with a
further 150 yds of safe water to port.
3 cables to run to the wheel over.
Recommend come right to new
course 095 to regain”