sail-world.com
 
 
News Home Cruising Photo Gallery Video Gallery

 

Sail-World.com : Back to basics: Seven Steps to Safer Sailing Navigation

Back to basics: Seven Steps to Safer Sailing Navigation

'Sailing navigation'    .

If you are anything like me, it's easy to forget your sailing navigation basics in exchange for the effortless nautical GPS or chart plotter. But if you want to excel as a sailing skipper, you need to keep a basic navigational chart plot going--just in case a spark blacks out your trusty black boxes!

Brush off those dusty navigation tools and use these super basic techniques to start off on the best foot for safe and sound sailing navigation.

1. Plot Your Latest Nautical GPS Position:.

Plot true courses onto your chart. Use arrow-heads to indicate direction. Label each course line as shown below (step six). Look at the nautical GPS or chart plotter. Enter the time, Latitude, and Longitude into a log book or binder. Plot this position onto the navigational chart.

2. Draw the True Course:

Use a protractor or parallel rules to draw the true course from the latest GPS position. On the compass rose, use the outermost ring and plot true courses. The true ring gives more accuracy, makes plotting easier on the eyes and stomach, and many charts only show true compass roses.

Label the course line with the Magnetic course. Use a magnetic course label, because you are steering the boat with a magnetic compass. To convert from a True course to a Magnetic course, you apply a correction called 'variation' to the True course. Subtract easterly or add westerly variation to the True course. Variation changes as your position changes, so make sure to check the variation often when sailing. Locate variation in one of two ways:

How to Find Variation on Charts Close to Shore:

Look in the center of the closest compass rose to your position. Near the crosshairs, the variation will be labeled with a number and the letters E (or East) or W (or West). Use the closest compass rose to your position.

Just below the crosshairs you will find a note of the annual increase or decrease in variation. Take the difference between the year shown and the current year. Multiply this difference by the minutes of increase or decrease. If increasing, add the difference to variation. If decreasing, subtract the difference. Round your answer to the closest whole degree of variation.

Example:

You find the closest compass rose to your position.
Variation: 18 degrees east (2004)
Annual decrease: 5 minutes

The current year is 2011; what is variation at this location?
7 (years) × 5 = 35 minutes
18 degrees east – 35 minutes = 17 degrees 25 minutes east

Round the answer to the closest whole degree. The variation in this instance is therefore 17 degrees east.

Sometimes the annual change in variation is noted as east or west, rather than increasing or decreasing. If the annual change has the same name (east or west) as the variation, variation is increasing. If the names are opposite, variation is decreasing. For example: If your compass rose says 12°14'W (10'E), this indicates a decrease of ten minutes a year because the names, W and E, are opposite. If it says 12°14'W (10'W), that would indicate an increase by 10 minutes a year because the names are the same.

How to Find Variation on Charts Offshore:

Sail further offshore and compass roses become less frequent. Because of this, you cannot rely on the compass rose on an offshore chart to show variation. Instead, look for diagonal, dashed, magenta colored lines--called 'isogonic lines'--that span the chart. Scan the line to find the variation written somewhere on the line. Use the variation shown on the closest isogonic line to your position.

Next, Find Your Magnetic Course.

Example: You plot a True course of 097 onto your chart. You look in the center of the closest compass rose or isogonic line to your position. You determine variation to be 7 E (East). Subtract easterly variation from True course to find Magnetic course. 097 True - 7E = 090 Magnetic.

To summarize, you plot the course in degrees true; you label the course line in degrees magnetic. Write the course label on top of the course line like this: 090 M (see illustration).

3. Average Sailing Speed Over Ground (SOG)

Under sail, speed can vary with the wind. So, to be effective, you will need to take an average of speed readings from your nautical GPS each hour. Average at least four speed readings. Write the speed label on the bottom of the course line beneath the magnetic label like this: S - 5 (see illustration).

4. Estimate How Far You Will Sail One Hour from Now:

Good sailing navigation means you will take your last position and 'project' it into the future. This method--called 'Dead Reckoning'--has been used for centuries for safety. By estimating where you will be ahead of time, you will have a solid reference to use for comparison to your next GPS position.

For instance, if you are plotting fixes every hour, estimate how far you will sail one hour from now. If your average sailing SOG was five knots, then you would estimate that you would travel five nautical miles over the next hour.

5. Measure your Distance Sailed:

Use dividers or better yet--a compass (this tool has a needle in one leg and a pencil lead in the other). Go to the right or left side of the chart (the Latitude scale). Spread the legs to your measured distance. In our example, we would spread the legs to five minutes of Latitude, which equals five nautical miles.

6. Plot the New Dead Reckoning (DR) Position:

Stick the needle part of the dividers or compass in your last known position (waypoint, light structure, or buoy). Sweep the other end of the dividers or compass over your sailing course. Place a pencil mark where it touches the course.

Plot a DR (dead reckoning) position as a half circle with a dot, ahead of your present position. This shows where you expect to be sometime in the future. Note that your 1200 position dot has been enclosed by a triangle. Some navigators prefer this to clarify the type of fix.

Electronic positions (GPS, radar) are surrounded by a triangle; visual bearing positions (taken with a compass) are surrounded by a full circle. Crystal clear labeling avoids confusion and creates a historical record of your vessel's path over the earth's surface.

7. Label Your DR Position:
Keep the navigation plot and all labels clear and neat for your sailing crew or partner. -  Captain John Jamieson?nid=91376  


Draw a half-circle over the pencil mark. Use just half a circle, because a DR position is a 'best guess'. Label the half circle with the time of the next fix and the abbreviation 'DR'. In our example, we measure 5 nautical miles ahead of the 1200 GPS position, place a dot and half-circle at that spot and label it as '1300 DR'. Now you know your approximate position one hour 'down-the-road'.

The Importance of a Logbook:

Keep a logbook. This should be standard procedure from the moment you get underway for a coastal or offshore passage until the moment you tie up. Keep separate sections for Navigation/Weather and Engineering. Log time, GPS, Visual, or Radar Latitude and Longitude, Course, Speed, plus weather information. Keep a comments section for information on sail changes or personnel situations (illness, injury).

Use the other section of the log book to record diesel engine information. Record hours, RPM, oil pressure, water temperature, fuel gauge readings, fresh water readings, and any engineering casualties or oddities (smoke, oil or fuel leaks).

Start all sailing navigation with a super basic dead reckoning plot like this. Gain the confidence you need for safer sailing--wherever in the world you choose to cruise!

John Jamieson (Captain John) with 25+ years of experience shows you the no-nonsense cruising skills you need beyond sailing school. Visit his website at www.skippertips.com for a free sailing tips newsletter. Become a member for instant access to 425+ articles, instructional videos, newsletters, e-Books, and live discussion forums.




by John Jamieson

  

Click on the FB Like link to post this story to your FB wall

http://www.sail-world.com/index.cfm?nid=91376

3:41 PM Thu 1 Dec 2011 GMT






Click here for printer friendly version
Click here to send us feedback or comments about this story.


News - USA and the World







Soling North American Championship concludes on Lake Erie by Canadian International Soling Association,






































Starboard Hatteras Wave Jam day 5 by American Windsurfing Tour,


















470 Men and Women Worlds - Champions decided in Santander by International 470 Class Association,




ISAF Sailing Worlds - Caleb Paine through to Finn medal race + video
ISAF Worlds - 49er, 49erFX, Finn and Nacra 17 Rio 2016 spots taken
ISAF Sailing Worlds - 470 Women's medal race images by Thom Touw
ISAF Sailing Worlds, Santander: Scott all set to lift Finn world title
ISAF Sailing Worlds - 470 Men's medal race images by Thom Touw
ISAF Sailing Worlds, Santander - Aussies and Austrians claim 470 gold
ISAF Sailing Worlds, Santander: 470 awards images by Sail-World.com
ISAF Sailing Worlds, Santander - 470 medal race images by Jesus Renedo
Annapolis-to-Newport Race - 'What to Expect' Seminar to take place
Royal Cup Marina Ibiza - No racing on penultimate day
Belcher takes record fifth 470 World Championship
ISAF Sailing World Championships - Santander - Day 8 video highlights
2014 Great Lakes Team Racing Championship about to set off
2014 Etchells North American Championship - Day 1
2014 U.S. Multihull Championship - Day 1
2014 Chicago Match Cup - Repechage top four determined in final flight
J/24 World Championship - 35th anniversary preview
470 Men and Women Worlds - Santander medal race line-up confirmed
ISAF Sailing Worlds, Santander - Day 8 images by Sail-World.com
Royal Cup Marina Ibiza - Quantum Racing stumbles in coastal race
ISAF Sailing Worlds, Santander - Americans ready for 470 medal races   
ISAF Sailing Worlds, Santander: Action ramps up with end zone in sight   
Big Boat Series - It's not the size, it's the length   
ISAF Sailing World Championships Santander - Double French RS:X gold   
ISAF Sailing Worlds, Santander - Day 8 images by Sailing Energy   
ISAF Sailing Worlds - Finn leaders emerge from shifty Santander breeze   
ISAF Sailing Worlds, Santander - RS:X winner images by Barbara Sanchez   
ISAF Sailing Worlds, Santander - Rio 2016 470 spots awarded   
52 Super Series 2015 - Outlook looks hot for the 52 Super Series   
Starboard Hatteras Wave Jam - Another early start on day 4   
ISAF Sailing World - First entry leaves sailor's reputation in tatters   
2014 Chicago Match Cup - Four go through to quarter finals   
470 Men and Women Worlds - Champs take over leaderboard   
ISAF Sailing World Champ - Buckingham finishes with career-best result   
America's Cup: Oracle's Larry Ellison to step down as CEO   
Classic Yacht Regatta - Sonny takes top classic prize   
ISAF Sailing Worlds, Santander - Buckingham finishes with career best   
ISAF Sailing Worlds, Santander - Rio 2016 RS:X spots claimed   
ISAF Sailing Worlds - Leaderboards shaping up in Santander + Video   
ISAF Sailing Worlds, Santander - Giles Scott continues to extend lead   


For this week's complete news stories select    Last 7 Days
   Search All News
For last month's complete news stories select    Last 30 Days
   Archive News







Sail-World.com  


















Switch Default Region to:

Social Media

Asia

Australia

Canada

Europe

New Zealand

United Kingdom


http://www.sail-world.com/event_images/image/Twitter_logo_small.png http://www.sail-world.com/event_images/image/FaceBook-icon.png  http://www.sail-world.com/event_images/image/RSS-Icon.png

United States

Cruising Northern

Cruising Southern

MarineBusiness World

PowerBoat World

FishingBoating World

 

Contact

Commercial

News

Search

Contact Us

Advertisers Information

Submit news/events

Search Stories/Text

Feedback

Advertisers Directory

Newsletter Archive

Photo Gallery

 

Banner Advertising Details

Newsletter Subscribe

Video Gallery

Policies

 

 

 

Privacy Policy

 

 


Cookie Policy

 

 



This site and its contents are © Copyright TetraMedia and/or the original author, photographer etc. All Rights Reserved.  Photographs are copyright by law.  If you wish to use or buy a photograph contact the photographer directly.
XLXL NEW US
LocalAds   DE  ES  FR  IT