GPS--Instant Navigation
2nd Edition

From Basic Techniques to Electronic Charting

By Kevin Monahan and Don Douglass

Published by .......
356 pages, 150 detailed diagrams ISBN 9780-938665-76-6 $19.95

"If you want the greatest possible benefit from GPS, I strongly recommend this book. Their illustrated techniques will save you time and clearly explain the system." - John Neal, Bluewater sailor,
Mahina Tiare

"Every GPS user should have this book on board!" - Captain Jack's Catalog

This Second Edition of the international best-seller "GPS--Instant Navigation", mariners will find simple solutions to navigational problems,  including modern GPS accuracy standards and expanded chapters on Electronic Charting and trouble-shooting.
Kevin Monahan is a retired Canadian Coast Guard officer with over 20 years' experience cruising the Inside Passage. Douglass has logged over 150,000 miles cruising from 60°N to 56°S. Includes 150 detailed diagrams, which graphically illustrate the many ways you can use GPS to solve classic piloting and navigation problems. This book introduces the novice to the basics of instant navigation and carries him to advanced techniques of error reduction, electronic charting, and navigation software.

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About GPS

The authors have witnessed the steady increase in capability of GPS technology and, after years of excellent performance, initial frustrations have given way to feelings of awe at its simplicity and accuracy. In describing techniques which allow a navigator to achieve high performance from GPS, we have tried to maintain a tie to traditional navigation techniques, yet capture the simplicity and responsiveness of GPS navigation. We have both considered it a challenge and a privilege to be able to develop some of the techniques described in this book, and to share them with each other when our blue-water paths crossed, as well as now, with you the reader.

Kevin Monahan and Don Douglass--From the Preface to GPS--Instant Navigation

It's not often you get something for nothing, but in this case, the incredible improvement in the accuracy of the satellite system comes at no extra cost to the user. As of midnight May 1, 2000 every GPS receiver in the world suddenly became more accurate, and more useful to the boating community.
Unassisted GPS can now compete with the accuracy of Differential GPS (DGPS) but, despite its phenomenal new accuracy, the differential GPS service still offers valuable enhancements where accuracy and reliability are critical. Clearly GPS is an emerging technology. With the introduction of a second civilian frequency in 2003, which will all but eliminate atmospheric propagation errors in the next generation of consumer GPS receivers, and with further improvements in the system beyond that, boaters can look forward to unparalleled navigational security.

Kevin Monahan and Don Douglass--From the Preface to GPS--Instant Navigation--Second Edition

Table of Contents

Quick Reference page
Preface to the Second Edition
Preface to the First Edition

CHAPTER 1 GPS Navigation Works!

What GPS Navigation Can Do for You
The GPS Receiver
The GPS Navigator
Startup: Initializing Your Receiver
Sidebar: The Other Fellow
Determining Where You Are
Summoning Help
How GPS Can Help You Return to a Man OverBoard (MOB)
Other Uses of the MOB Function
How GPS Helps You GOTO Your Dock
GPS Setup Menus
Hand-held GPS
How GPS Works
A Brief History of GPS
Where to Find Current Information on GPS
Getting More Out of Your GPS: the Next Step

CHAPTER 2 Basic GPS Navigation

Why Use a Nautical Chart?
Reading a Nautical Chart
Latitude and Longitude
Taking a Position off a Chart
Plotting a Position on a Chart
Direction and Magnetic Variation
Plotting an Approximate Position
Dead Reckoning (DR)
Course and Speed
Sidebar: Time, Speed, and Distance
Search and Rescue

CHAPTER 3 GPS Errors and Insights

Precision and Accuracy
The Dockside Test
Sidebar: New GPS Accuracy Standards
Error Circles
Repeatable Accuracy and Loran C
The Workbook
Course and Speed Error
GPS and the Nautical Chart
Chart Datum
Converting from One Chart Datum to Another
Unknown Chart Datum
Sidebar: CBC Radio News: 21 Dec. 1998
Universal Transverse Mercator Maps (UTM )
Operating Near the Magnetic Poles

CHAPTER 4 Waypoint Navigation

The Destination Waypoint
MOB (Man Over Board) Revisited
Sidebar: Cecil’s Style of Navigation
Navigating to a Single Waypoint (GOTO)
Sidebar: Keeping a Waypoint Log
The Saved Waypoint and Waypoints Entered
by Present Position
Returning to a Saved Waypoint
Entering a Waypoint by Latitude and Longitude
Practicing With Your GPS Navigator
Default Hemisphere
Entering a Waypoint by Range and Bearing from
the Present Position
Entering a Waypoint by Loran C Time Differences (TDs)
Updating a Waypoint
En-route Functions
The Steering Diagram
Customizing the Steering Diagram
Following the Steering Diagram
Sidebar: The One in Sixty Rule
Waypoint Realization
Avoidance Waypoints
Waypoints and Chart Datum
Alarms and Alarm Zones
Anchor Watch Alarm
Sidebar: Chart Datum Conflicts
Cross Track Error (XTE) Alarms and Boundary Limits
Data Input

CHAPTER 5 Route Navigation

What Is a Route?
Creating a Route (Setting up a Route)
Verifying Waypoints in a Route
Waypoints within a Route
Starting Route Navigation
Following the Route
Arrival Radius and Waypoint Realization
Saved Routes
Selecting Waypoints
Curvilinear Legs

CHAPTER 6 Navigation Techniques Using Position, Course, and Speed

Using Lines of Latitude and Longitude as a Quick Reference
LOPs and Safety LOPs
Limiting Lines of Latitude and Longitude
Determining Course Made Good (CMG) and Speed Made Good (SMG)
Sidebar: Making a Landfall
Checking Your Compass
Determining Speed Through the Water and Checking the Speed Log
Sidebar: Parallax
Route Execution Using Combined Techniques

CHAPTER 7 Waypoint and Route Navigation—Advanced Techniques

Navigating in Tight Quarters
Determining CMG and SMG Using Waypoints
Finding the Set and Drift of the Current Using a Dead Reckoning (DR) Waypoint
Routes and Currents—The Hooked Course Line
Using Cross Track Error (XTE) to Fix Position
Using Range and Bearing of a Waypoint or GOTO to Fix Position
Using a Chart of Unknown Datum
Using Waypoints to Show Military Area, International, and Fishing Boundaries
Using Two GPS Navigators
Great Circles and Rhumb Lines
Sailing with GPS

CHAPTER 8 Enhancing Your Understanding of GPS Accuracy

GPS Error Averaging
Ionospheric and Tropospheric Refraction
How the New GPS Accuracy Affects Navigation
Predicting Error Using Horizontal Dilution of Precision (HDOP)
Simultaneous or Multiplexing GPS
Satellite Masking
Multipath Errors
Antenna Height
The Ideal Antenna Installation

CHAPTER 9 Differential GPS (DGPS)

What Is DGPS?
DGPS Coverage
Sidebar: DGPS for Land Surveying
Another Dockside Test
Fringe Reception Areas
Update Delay—High-Speed Navigation
Sidebar: HM Submarine Tireless
Navigational Notices
Sidebar: WAAS and NDGPS
DGPS in the British Isles
The Future of DGPS

CHAPTER 10 GPS Plotters

Simple Plotters
The GPS Sensor
Getting Used to the Display
Working With Waypoints and Event Marks
Horizontal Datum
Using Event Marks to Identify Danger Areas
Anchor Watches
Retracing a Course Line
Working with Limiting Lines
Chart Plotters
Sidebar: Search Patterns
The Effects of Smoothing
Perils Associated with DGPS Update Delay

CHAPTER 11 Electronic Charting Systems

Introduction to Electronic Charting Systems (ECS)
PC Cards
Self-Contained Systems
Electronic Charts (ECs)
The Dockside Test (Again)
COG and Heading Vectors .
The Vessel Icon
The Vessel Track
Automatic Chart Selection
Chart Insets (Plans)
Dynamically Linked Notes
Drawing on an Electronic Chart
Entering Waypoints
Working with Routes
Using Range Circles
Using Ship-Centered Bearings
Update Delay Issues with DGPS
Event Marks and Text Storage
Other Types of Marks
Boundaries and Guard Zones
North-up and Course-up Modes
Head-Up Mode
Radar Overlay
DR Simulation Mode
Recording Local Knowledge
Packaged Programs
Uploading Routes to a GPS Navigator
Importing and Exporting Routes
Open Navigation Format
Updating Electronic Charts
Photo Charts
Bathymetric Charts
Shipboard PC Specifications
Sidebar: Keep Those Paper Charts!
ECS Caveat Emptor (Let the Buyer Beware)
Sidebar: Computer “Crash” on the Sailing Vessel Xephyr
The Future of Electronic Charting

CHAPTER 12 When GPS Fails

Types of Failure
Old Data
Cues and Clues
Causes of Failure
Protect Yourself
Other Navigational Aids

CHAPTER 13 Advanced Systems

National Marine Electronics Association (NMEA) 0183 Standard
Autopilot Interface
ECS and Autopilot
Sidebar: GPS/Autopilot Interfaces in Small Vessels: The Devil’s Work?
Radar/ARPA Integration
Sidebar: CANStar
Electronic Chart Display and Information Systems (ECDIS)
Sidebar: ECDIS on the Saint Lawrence River


A. Decimal Minutes vs. Seconds
B. GPS and DGPS Internet Sites
C. Units in Use and Conversion Factors
D. Incidents
    Royal Majesty
    Salty Isle
E. Sample Waypoint Log
     Sample Route Log
F. Compensating for Current
    Finding the Set and Drift of the Current
    To Counteract the Effect of Current
G. List of Horizontal Datums
H. GPS Time and Clock Bias
I.   GPS Features—Good and Bad

Bibliography and References
The Workbook
Fine Edge Nautical Publications
About the Authors



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Last updated August 2023