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Summary
In this activity, students explore the importance of charts to navigation on bodies of water. Using one worksheet, students learn to read the major map features found on a real nautical chart. Using another worksheet, students draw their own nautical chart using the symbols and identifying information learned.
Learning Objectives
After this activity, students should be able to:
Understand fundamental differences between navigation on land vs. navigation on water.
Identify major features and read the essential symbols and information provided on nautical charts.
Materials List
Each student needs:
1 copy of each of the two activity worksheets
Colored pencils, markers or crayons (red, green, purple)
Introduction/Motivation
If you were floating on a boat on the ocean how would you find your way back home? Ask the students to suggest ways that a person could find his/her way if s/he is traveling by boat?
We are all familiar with maps that help us find our way as we walk, bike or drive in our own town or in a new city. Ask the students if they've ever seen a map for traveling on water. How would that map be different than what you would use if you were traveling by car? (Possible answers: No roads, sidewalks, street signs are available on the water. You would want to know the water depth, the location of bridges, lighthouses and harbors, the location of underwater obstacles [rocks, shipwrecks], etc.)
Maps that are used by people who are navigating on oceans, lakes, rivers (any body of water) contain helpful locator information, just like maps used on land. Maps used for navigating on water are called navigational charts.
Today we're going to look at a real nautical chart and learn to read its symbols and information. Then, we're going to draw our own navigational charts, using the same types of symbols and identifying information.
Describe how using the information provided on nautical charts can help find your location and navigate on water.
Procedure
Background
Sea Navigation
We have all traveled by car or on foot; it is easy to understand. But, what about traveling by sea? The sea is open and barren with no distinctive features. Dead reckoning is a very important skill for knowing where you are when traveling by sea. Because environmental conditions, such as sea currents or wind, can cause errors when using dead reckoning, it is important to look for landmarks. But, there are no natural landmarks on the sea. Luckily, people have made landmarks for us.
Aids in Sea Navigation
What other types of information would be helpful to know? What if you are traveling in a bay that is very shallow? You would want to know how deep the water is so that you do not run aground and damage your vessel. There are few natural landmarks that can be used. For this reason, people have made landmarks to use for navigating on water. Examples include:
Buoys: These floats with a bell or light are moored (anchored) in water. They are used as a landmark, a warning of danger, or a marker of a bay or channel.
Lighthouse: A tower with a bright, rotating light, located on or near shore to inform a sailor that land is nearby. Lighthouses are especially useful at night or in bad weather, when one's sight is limited. For example, a sailor could easily run into land if s/he could only see a distance of 20 feet.
Beacons: A generic term for some sort of sea landmark, such as a buoy or lighthouse.
Old shipwrecks: Ships do sink, and you definitely want to avoid them so that you do not sink your vessel also.
Nautical Charts
Land maps are not very useful when you are on the sea. Special maps designed for traveling by sea are called nautical charts. Some of their features are:
Depth: Nautical maps show depths under the water surface, just like topographical maps show elevation on the ground. Ship captains use these maps to avoid shallow areas or shipwrecks that could damage their ships.
Shoreline: Sailors like to know where land is located.
Landmarks: Such as shipwrecks and beacons.
Magnetic declination: Sailors must know the difference between true north and magnetic north, so that they can navigate properly.
Routes: Nautical maps show shipping lanes, and common and safe routes for sea vessels. Sailors use these lanes just like drivers use streets. Shipping lanes avoid shallow areas that can damage (or even sink) ships.
Currents: Nautical maps show the general direction in which the current flows at various locations.
A portion of a nautical chart showing land and water areas, marked with depth contour lines, depths, a directional compass, and identifiers for beacons and landmarks.
Figure 1. A section of the nautical chart for the San Francisco Bay in California.
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