How to Read Latitude and Longitude on a Nautical Chart
How to Plot Latitude and Longitude on a Nautical chart
Any GPS receiver will find the latitude and longitude along your sailing routes at any moment. But as a skipper, take yous plotted this data onto a navigational chart to check your position?
At 1030 y'all obtain the following position from your GPS: Latitude 41°17.0'N; Longitude seventy°26.0'W. Follow the steps beneath to come across how yous would plot this 1030 GPS position.
Fast Review to Become You lot Started
Cartographers (chart makers) create a filigree-like web on your nautical chart. Latitude lines run in a horizontal direction. Longitude lines run in a vertical direction.
Navigating with Latitude.
Imagine the earth, balanced on her axis without a tilt. Wrap a "chugalug" around the earth, divide information technology in ii and you have the equator--birthplace of Latitude. Label the equator 0 degrees (0°).
Breadth lines parallel the equator to the north or to the south. To find latitude, you lot measure how many degrees you are n or south of the equator. Latitude reaches a maximum of 90 degrees (90°) at both north and south poles. Ever label Latitude North, if north of the equator, or South, if s of the equator.
In chart navigation, use the scales on the right or left side to notice latitude. These scales are cleaved down into degrees, minutes and tenths of a infinitesimal, or degrees minutes and seconds. One caste of breadth equals sixty minutes; one infinitesimal of Latitude equals sixty seconds.
ane° = sixty'
1' = 60"
If your nautical chart shows degrees, minutes and seconds, change the seconds into tenths of a minute. When navigating, information technology's much easier to work with degrees, minutes and tenths. To do this, divide the number of seconds by 6. Follow these two examples:
Catechumen 42° 25' 18" N
18" / 6 = 0.iii'
Latitude: 42° 25.3' N
Catechumen 16° 09' fifty" Northward
50" / 6 = 0.8' (rounded off).
Latitude: 16° 09.8' N
Navigating with Longitude.
Return to your imaginary globe. To measure out Longitude, you again divide the world in half, merely this time lengthwise. Locate Greenwich, England on your globe. Draw a line effectually the earth that intersects Greenwich and both north and s poles. Cartographers call this the Greenwich, or prime number height--the birthplace of Longitude. Characterization the Greenwich peak 0 degrees (0°).
Longitude lines parallel the vertical Greenwich peak to the e or to the west. To discover longitude, you mensurate how many degrees you lot are east or west of the Greenwich acme. Longitude reaches a maximum of 180 degrees (180°) on the other side of the world, at the International dateline. You lot must label Longitude E, if east of Greenwich, or West, if west of Greenwich.
Apply either the top or bottom of the chart to measure out Longitude. Like Latitude, Longitude is broken down into degrees, minutes and tenths of minutes or degrees, minutes and seconds. Use the same methods shown before to catechumen seconds to tenths of a minute.
Even with advanced electronics, all skippers must however be able to observe latitude and longitude the traditional mode. This will make your sailing navigation more accurate and you lot will always exist able to encounter your vessels position on a nautical chart.
How to Plot Your Position With Super Accuracy
Imagine that you look at a chart without whatever land or water areas. All of the buoys, lights, towers, tanks, and nautical chart symbols disappear. You lot are left with merely a grid over your nautical chart that has lines that sew and downward and left to right.
Those that run left and right (or eastward and due west) are lines or parallels of Latitude. Those that sew and down are lines or meridians of Longitude. These lines class a series of grids over your nautical chart.
At whatsoever moment in time, your sailboat will be located in one of those grid boxes--called a "position box". Your get-go pace will be to locate your specific "position box". Follow these like shooting fish in a barrel steps:
Tools You Will Need.
* Nautical chart. * Direct edge. * Plotting (draftsman) compass. * #2 pencil.
Locate Your "Position Box" Before You Plot! (Illustration A above)
ane. Write down your GPS Latitude and Longitude into your log.Label each coordinate Northward or S (for Latitude) and E or West (for Longitude). In the illustration above, y'all write down Latitude 41°17.0'N; Longitude seventy°26.0'W.
2. Concentrate on illustration A. Look at the right or left side of the nautical chart--the Latitude calibration.
three. Locate the approximate latitude 41°17.0'N. Find that it lies between 41°10.0'N and 41°20.0'North. on the right side of analogy A. Place your finger at about this location on the right side of the nautical chart.
iv. Scan the top or lesser of your nautical chart and notice the approximate location of your Longitude 70°26.0'Due west. Detect that it lies betwixt seventy°20.0'W and 70°30.0'West on the bottom of analogy A. Place a finger from your other hand at this location.
5. Sweep your finger across the chart horizontally along your approximate latitude. Sweep your finger vertically along your estimate longitude.
six. Terminate when both fingers intersect in the torso of the chart. You are now within your "position box".
7. Mark the corners of your box with a pencil as shown in illustration A. That way, if you lot need to leave the chart for any reason, you will exist able to come right back to your position box to consummate your plotting. Now go to the next fix of steps below to complete the plotting of your position: 41°17.0'N; seventy°26.0'W.
Find Your Exact Position Fast! (Illustrations B, C, and D above)
1. Find the bottom edge of your "position box". Follow that Breadth line over to the right or left side of the chart.
2. Button the needle point of your compass in that line on the correct or left side (latitude scale) of the chart. Notice in analogy B, you lot stick the needle point in the line marked 41°10.0'N. Next, spread the compass open until the pencil lead touches the exact latitude of your position. In illustration B, we spread the compass open until the pencil lead touches 41°17.0'Due north.
3. Lift the compass off the side of the nautical chart. Take care not to change the spread of the compass. Motion over to your "position box".
4. Stick the compass needle in the lower corner on one side of the "position box". Sweep the compass pencil pb over the vertical line of the box. Make a small arc (mark). Repeat this on the lower corner on the opposite side of the box. Utilize a straight edge to draw a line from arc to arc as shown in illustration B.
5. Find the right or left edge of your "position box". Follow that Longitude line upwardly or down to the acme or bottom (longitude scale) of your chart. In analogy C, we take followed the correct edge down to the longitude scale.
6. Stick the need point of the compass in the longitude line yous followed down--in this example 70°xx.0'W. Next, spread the compass open until the pencil lead touches your exact longitude of lxx°26.0'Due west.
7. Elevator the needle point just off the longitude line and follow that same line dorsum to your "position box". Stop when you get to the penciled line that you drew (stride four). Push the needle point of the compass into the chart where the penciled line starts. Sweep the compass lead over the penciled line. Mark your position as shown in illustration D. Erase all extra lines and marks to neaten the plot.
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Exercise sound sailing navigation techniques like these and yous will get a more confident skipper, set for whatever comes y'all way. You will have the peace-of-mind and know-how when the chips are down to find you lot fashion home--wherever in the world you choose to cruise!
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