Azimuth and Altitude

Introduction: When finding our way through the landscape, we use points of reference to orient ourselves. At sea, navigators use azimuth or bearing to describe the direction and altitude to describe the height of the sun or a star, lighthouse, or buoy used as a point of reference.

What to Expect: After practicing the skills in the classroom, take the class outdoors for experience using the skills in the real world.

Materials: Compass, General Star Map

Procedure:

PART I

1. Introduce the compass and the 360 degrees of circle. It is helpful to use an overhead projector and show a circle marked clearly in 360°. You can place a clear compass on the overhead projector and show how the needle continues to point north, even when the housing of the compass is rotated.

2. Pass out as many compasses as possible. Have students stand and face north, using the compass to confirm the direction. Remind them that north is also described as 0° or 360°. The students should then face east (90°), south (180°), and west (270°), using the compass to check their direction. At each direction, students should choose an object to focus on that is directly ahead when they are facing the correct direction.

3. Let individuals choose a direction for the class to face, calling it out in degrees. Again, students should choose an object straight ahead when they are facing that direction. Explain that the direction you look to see an object is called its azimuth or bearing; the process is called “taking a bearing”.

4. Now have a student call out an object and let other students give its azimuth. They should give the direction, in degrees, that they look to see it.

5. Try this exercise in a different location, outdoors if possible.

6. Have the students move until an object is at a certain azimuth. For example, tell them to stop walking when the flagpole bears 125° (when the azimuth of the flagpole is 125° ).

7. Have students take bearings on two different objects on the school grounds, then exchange information and have other students find the place where they were standing.

PART II

1. Have students stand and put a fist at eye level with arm extended. The bottom of the fist stands for the horizon, altitude of 0°.

2. Have students count nine fists, placing one fist on top of the other. Every student should find that the ninth fist ends up straight above his/her head, altitude 90°, or zenith. In this way, students have used their bodies to find altitude. Each fist equals 10° of altitude.

3. Discuss the following ideas with the students:

• You have a ready-made height-measuring device with yourself at all times.
• This method works because humans tend to be proportional and distances are great between objects being measured.
• You can find the North Star (Polaris) by using the Big Dipper’s pointer stars.
• If you find the altitude of Polaris, then you know your latitude; degrees of altitude of Polaris equal degrees of latitude in Northern Hemisphere.
• If you can find Polaris, then you should be able to find any planet, star, galaxy, or nebula in the night sky using instructions that give the object’s azimuth, altitude, and time of viewing.

Evaluation:

1. Ask students to find the azimuth and altitude of assigned objects outdoors when standing at a preselected location. Flagpoles, treetops, chimneys, and the moon are useful for this; the sun should not be used since students could damage their eyes looking at it.

2. Students should be able to find the azimuth and altitude of the moon, Polaris (North Star), or a planet at a certain time of night.

Extensions:

1. Assign objects to observe in the night sky. The best viewing is found away from bright lights and with a distant, flat horizon for accurate measurements of altitude.

2. Use these exercises with a unit on maps. Have the students use the bearings of objects to construct maps of the school grounds or their yards at home.

3. Use these exercises with a unit on astronomy to help students locate objects of interest in the night sky.

4. Students can make a simple height-measuring device using the GEMS guide “Height-O-Meters”. This is available through National Science Teachers Association.