Parallel Index Technique in Restricted Waters

Published Date

March 2014


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Parallel Index Technique in Restricted Waters

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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

assignments.

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.

Foreword

Preface

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

This book underlines the most common errors and limitations that affect parallel indexing and have been observed by pilots of the Corporation of the Lower St Lawrence (CLSLP) during their assignment.

Title: Parallel Index Technique in Restricted Waters
Number of Pages: 112
Product Code: WS1426K
ISBN: ISBN 13: 978-1-85609-619-5 (9781856096195), ISBN 10: 1-85609-619-X (185609619X)
Published Date: March 2014
Binding Format: Paperback
Book Height: 275 mm
Book Width: 215 mm
Book Spine: 5 mm
Weight: 0.10 kg
Author: Alain Victor

Customer Reviews

This book fills in the gap between basic awareness of potential errors and how they will affect and be observed onboard when monitoring passages Review by By Captain Kevin Vallance Deep Sea Pilot and Young
From the beginning of their training process of how to use radar, including the basics of radar observation and plotting techniques, all mariners should have been made aware of the errors and limitations that can, and do occur with the equipment. In more recent years the need for vessels to always follow pre-planned dynamic passage plans should have been taught and appreciated.

When properly planned and constructed the use of parallel index techniques is an excellent tool to enable the continuous monitoring of the passage, particularly when operating in restricted waters. However, it is of vital importance to appreciate how the errors and limitations of the radar equipment will impact upon this position fixing and monitoring.

This book fills in the gap between basic awareness of potential errors and how they will affect and be observed onboard when monitoring passages. Practical real life situations are illustrated throughout the book which demonstrates that these are not just theoretical or academic possibilities but they are in fact present a series of potential navigational pitfalls that the person conning the vessel must be aware of to help prevent possible grounding errors.

By Captain Kevin Vallance Deep Sea Pilot and Younger Brother of Trinity House. (Posted on 01/09/2014)

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