• The student will be able to state the main idea of a story.
• The student will be able to define some boating terms.
• The student will be able to define magnetic north, true north, and magnetic fields.
• The student will be able to explain why compensation must be made when transferring a compass reading onto a map.
• The student will be able to carry and borrow when adding or subtracting degrees and minutes.

Materials

• Compass worksheet (1 per student)
• Compass worksheet answer key
• Vocabulary worksheet (1 per student)
• Vocabulary worksheet answer key
• Story
• chalk and board or clean transparency
• overhead projector
• Overhead of worksheet
• Overhead pens

Outline

1. Read the lesson on compass use and play the game. This will give you a thorough understanding of the material to be taught.
2. Start by stating that you are going to tell a humorous story.
3. Explain to the students what a GPS is. Explain that a GPS is a navigational aid. It uses satellites to know where it is. Put in your destination and it will tell you the compass course to follow to get there. If you don't know how to read a chart, but still want to sail a GPS will let you do so.
4. Tell students that you want them to listen carefully and then tell you what the problem was.
5. After you have finished the story ask the students for their ideas. Write their ideas on the board as they give them to you. The main idea you want is that the ship didn't know where it was (navigation error) on a chart. Hint, to the students, that the crew didn't know how to do the corrections that you are going to teach them how to do today.
6. Tell the students that today they are going to learn 1) how a compass can be affected by metal, 2) what true north is, and 3) how to correct for these things.
7. Handout the vocabulary worksheet with instructions that it will be gone over in class.
8. See how many of the words the students can correctly match to the definitions, by discussing each term and definition as a class.
9. Collect the Vocabulary worksheet.
10. Explain how a compass works and why metal affects it. Ask your students to tell you why mounting a compass on a boat might affect it's reading. You want them to realize that a boat has metal parts to it and on it. Don't forget the metal they wear can be a handy teaching aid; point out someone with a metal belt buckle and ask if they would get the same reading from the compass as someone sitting next to them without a metal belt buckle.
11. Explain the difference between true north and magnetic north. Explain that charts (and maps) are set up to have true north at the top of the map; therefore, it becomes necessary to adjust a ships heading for the way the compass reads.
12. Here you can use the overhead or board to draw a line for true north. Then draw another line starting at the same point for magnetic north. Ask the students what would happen if they tried to follow a compass reading, without correction, in relation to true north. They should see that if the variation is to the west then they would have to add the variation to their compass to wind up where they wanted to go, and just the opposite for east.
13. Explain the mechanics behind adding and subtracting degrees and minutes. Show them how to barrow and carry.
14. Hand out the worksheet and turn on your overhead to show the worksheet. Go over the first example, with the class, and one of the harder ones if needed. Then let the students work the rest of the worksheet on their own.
15. Collect the compass worksheet.
16. In closing remind them of how embarrassed the captain must have been. Ask the students what would happen if they were in a narrow passage, on a boat, in the fog, and they added instead of subtracting for the error. You should get that they would run aground.

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