Parallel Index Techniques in Restricted Waters. Incl. RADAR Errors and Limitations. Use of ARPA and Chart Overlays (2nd Edition) (eBook)

Published Date

August 2020

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Parallel Index Techniques in Restricted Waters. Incl. RADAR Errors and Limitations. Use of ARPA and Chart Overlays (2nd Edition) (eBook)

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This book is a guide to best practice for parallel indexing in restricted waters. It highlights

the most common errors and limitations that affect parallel indexing which have been

observed by pilots of the Corporation of the Lower St Lawrence Pilots (CLSLP) during their


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Parallel indexing is a well established method of constantly monitoring a vessel’s position.
In marine navigation, the main goal of radar is to detect any vessels in the vicinity of the ship or any obstacles, such as land masses, in reduced visibility. Radar is also widely used in good visibility.

Technological improvements and development refinements have allowed users to stretch the use of radar to its limits.

The purpose of this book is to explain how it can be done safely.



1 Introduction

2 Relative Stabilised Presentation, Quick Review

2.1 Characteristics

2.2 Advantages when using parallel index technique

2.3 Disadvantages

3 Relative Unstabilised Display

4 True Motion

5 Word of Caution

6 Principles of the Parallel Index Technique

7 Relation Between ROT, SMG and Radius of Turn

7.1 Worked Example

7.2 How to Quickly Find the Centre of a Turning Circle?

8 Beam Width Distortion and Effect on Parallel Index Technique

8.1 3 cm RADAR Beam Widths (Approximate and Calculated)

8.2 Calculated Beam Widths for 10 cm RADAR

9 Range Scale 3 Miles, Beam Width Effect Alone

10 Important Remarks

11 Measuring Beam Width

12 Measuring Beam Width without Buoys or Information in a Ship’s Manual

13 Improper use of PI Technique

14 Practical Examples of being in a Channel

15 Example with Land Target Abaft the Beam

16 Effect of Echo Enhancing

17 The “Total” Method

18 Range Error or RE

19 Ship Alongside

20 Detecting RE without Quantifying it

20.1 Under Ranging

20.2 Over Ranging

20.3 Blind Circle

21 Collateral Effect of RE on PI Technique

22 Adjusting and Using PI Technique when RE is Known

23 Heading Marker Alignment

24 Practical Example of HM Misalignment

25 Gyro Error and Effect on Parallel Index Technique

26 Practical Example

27 Error Analysis in Reduced Visibility

28 When not to use Parallel Index Technique

28.1 Final Orientation

28.2 Gyro Lag

28.3 Gyro Drift

28.4 Substantial RE

29 Analogue Radars (CRT)

29.1 Non-Linearity

29.2 Velocity Error

29.3 Ovoid Rings

30 Radar Repeater

31 Radar Check (Example)

32 COG Vector Derived from GPS Displayed on Radar

33 Extremely Important

34 AIS and Anti-Collision

35 Some Myths

35.1 Port Side of a Target

35.2 Measuring RE

35.3 Measuring RE with PI Lines

35.4 Effect of Beam Width Alone if not Accounted for

35.5 Effect of Beam width Properly Accounted for

35.6 Heading Marker Slewed 2° to Port

35.7 One Side Only

36 Conclusion

37 References

Appendix 1 ECDIS and Radar Answers

Appendix 2 AIS Position Discrepancies

Appendix 3

Title: Parallel Index Techniques in Restricted Waters. Incl. RADAR Errors and Limitations. Use of ARPA and Chart Overlays (2nd Edition) (eBook)
Product Code: IT102980
Published Date: August 2020

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