SailNet Community - Reply to Topic

   Search Sailnet:

 forums  store  


Quick Menu
Forums           
Articles          
Galleries        
Boat Reviews  
Classifieds     
Search SailNet 
Boat Search (new)

Shop the
SailNet Store
Anchor Locker
Boatbuilding & Repair
Charts
Clothing
Electrical
Electronics
Engine
Hatches and Portlights
Interior And Galley
Maintenance
Marine Electronics
Navigation
Other Items
Plumbing and Pumps
Rigging
Safety
Sailing Hardware
Trailer & Watersports
Clearance Items

Advertise Here






Go Back   SailNet Community > Skills and Seamanship > Learning to Sail > How do I read my chart scales?
 Not a Member? 


Thread: How do I read my chart scales? Reply to Thread
Title:
  

By choosing to post the reply below you agree to the rules you agreed to when joining Sailnet.
Click Here to view those rules.

Message:
Trackback:
Send Trackbacks to (Separate multiple URLs with spaces) :
Post Icons
You may choose an icon for your message from the following list:
 

Register Now

In order to be able to post messages on the SailNet Community forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
Please note: After entering 3 characters a list of Usernames already in use will appear and the list will disappear once a valid Username is entered.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Click here to view the posting rules you are bound to when clicking the
'Submit Reply' button below


Additional Options
Miscellaneous Options

Click here to view the posting rules you are bound to when clicking the
'Submit Reply' button below


Topic Review (Newest First)
05-29-2010 11:10 AM
svHyLyte
Quote:
Thanks a lot guys! Definitely a lot of help, and I do plan on taking classes...just a matter of time and money!
See United States Coast Guard Auxiliary - District 11NR

Contact the Sacramento Flotilla at Bob@themccaws.com

CGA Classes are very inexpensive.

FWIW...
05-28-2010 06:51 PM
jackdale You you would like some free online information you might look at:

Advanced navigation courses - sailing schools Greece and the Greek islands

Just remember that the aids to navigation section is based on IALA system A (red right leaving). You live in system B (red right returning)
05-28-2010 06:33 PM
Hays Thanks a lot guys! Definitely a lot of help, and I do plan on taking classes...just a matter of time and money!
05-27-2010 10:42 PM
tomandchris If you are going to do coastal work, read a book, read your charts, and have a good GPS. If they all agree, go sailing. If you are crossing a very large bay or ocean do more.

First....go sailing!
05-27-2010 12:21 PM
Yamsailor or take an American Sailing Association or USSAILING Coastal Navigation class.
05-27-2010 11:54 AM
jackdale
Quote:
Originally Posted by Vasco View Post
Don't use the scale to measure nautical miles. Use the latitude marks at the side of the chart. A nautical mile (one minute of arc) varies in length (feet) depending on the latitude so you should always use the latitude marks.

A nautical mile varies in length from 6040 feet at the equator to 6108 feet at the pole. The mean length is 6080 feet and this is the standard nautical mile.
Agreed about using the latitude scale. The scale shown by the OP is probably based on the scale shown in the title block which is based on a parallel of latitude which might not actually be on the chart. As an example the 1:80,000 chart that I use to teach coastal navigation is accurate at 49 30' N which not actually on the chart.

A nautical mile is defined as 1852 meters.

Quote:
INTERNATIONAL NAUTICAL MILE. The international nautical mile is equal to 1852 metres (6076.1 feet). For practical purposes, the sea mile is used for expressing distances. A sea mile is the length of one minute of arc, measured along the meridian, in the latitude of the position.
05-27-2010 10:06 AM
svHyLyte Hays--In your effort to learn to sail it would be wise to take some of the Cost Guard Auxillary classes and particularly, in this case, the class on coastal piloting and navigation. You might also amble over to the West Marine store (there's no shortage of those in the Bay Area) and pick up one of the books on the subject.

At the scale of the Chart's you're using for sailing in the Bay, using the distance scales on the bottom corner of the chart (which I guess are chart-kits) is perfectly adaquate for measuring purposes. The "10ths" scale on the left side of the scales is to allow you to step off distances with a divider. First set to a whole measure of miles (nautical or statute) which is walked off along a course line and then, the last distance measured on the 10th's scale. Knot meters/logs and GPS devices are normally graduated in knots or nautical miles hence the nautical mile scale is normally the most useful for your speed/distance/time computations. For the sake of convenience, remember that a 10th of a mile is about 200 yards.

FWIW...
05-27-2010 10:00 AM
sailingdog Vasco— The scale on a chart should be reasonably accurate over its entire area...

As Mawn has pointed out—the green dot is the same distance from the yellow or blue dots and can be used to determine distances. The reason for the side to the left of the green dot is so you can read/measure tenths of a mile.
05-27-2010 09:41 AM
tomandchris Hays,

The scale of this chart is for a somewhat small area. Therefore the longer NM.

On your example, blue to red, and red to green are each 1/2 NM, and each of them is divided into 1/10 NM. Green to yellow is 1 NM.

So, dependent on what you are using to measure NM, and a protractor works as well as anything, you have a scale that that can be translated. If something is 5.7 NM, you will move the protractor adjusted at 1NM five times and then adjust it to the balance of your distance and measure against the 1/10 scale. Clear as Mud?
05-27-2010 07:46 AM
Vasco Don't use the scale to measure nautical miles. Use the latitude marks at the side of the chart. A nautical mile (one minute of arc) varies in length (feet) depending on the latitude so you should always use the latitude marks.

A nautical mile varies in length from 6040 feet at the equator to 6108 feet at the pole. The mean length is 6080 feet and this is the standard nautical mile.
This thread has more than 10 replies. Click here to review the whole thread.

 
Posting Rules
You may post new threads
You may post replies
You may post attachments
You may edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On


All times are GMT -4. The time now is 07:41 PM.

Add to My Yahoo!         
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
SEO by vBSEO 3.6.1
(c) Marine.com LLC 2000-2012

The SailNet.com store is owned and operated by a company independent of the SailNet.com forum. You are now leaving the SailNet forum. Click OK to continue or Cancel to return to the SailNet forum.