When looking at latitude lines on a map or a globe it is hard to understand that they are angle measurements and that is why their unit is measured in degrees. The lines are clearly parallel. In fact, that’s another word for latitude lines…parallels. So, students are rightfully confused about the angle connection. I find these two online simulations helpful when explaining to students how longitude and latitude are measured.
What’s even more helpful is for students to do some hands on exploration with a 3 dimensional model. These were pretty easy to make. I became inspired after I accidentally ordered hemispheres instead of full spheres when I was making earth models. After brainstorming about what in the heck could I use these for, I thought they would be perfect for modeling how latitude and longitude lines are angles. Below are the instructions for making them. Either you can prepare them beforehand or students can make the themselves. I think it’s most useful to have students work in pairs.
- Purchase hemispheres**
2. Use a marker to mark the equator.
3. Cut a piece a yarn about 12 inches. Tie one end around a paper fastener. Double knot it.
4. Push the fastener in the middle of the flat hemisphere and cut the little part still hanging out. It might be helpful to hot glue the fastener in the middle. Now notice how you can create an angle with the equator. We want the students to notice that too!
5. The next step takes a little dexterity. A partner and some thumbtacks make it a little easier. The thumbtacks will also serve as “cities” on the same latitude line. Where the red yarn meets the arc, try making a little notch there with scissors. (By the way, this is a randomly made angle. It doesn’t matter what angle the students choose.) Then, wrap the rest of the yarn around the circle and back to the middle making the same angle (we’ll measure those angles with a protractor in the next step to make sure they are the same size). Holding the yarn down with thumbtacks as you wrap it around does help and then serves as “cities” on the same latitude. I then twist the excess string around the middle fastener to hold the angle shape so we can measure it with a protractor. Have students explore different angles and you assess whether they are correctly identifying the latitude. For example, the picture below is about 40 degrees south of the equator. So the thumbtacks representing the cities would say their latitude is 40 degrees south.
6. Showing longitude: Now, since this is only a hemisphere, students choose whether the round side will represent east of the Prime Meridian or west. It’s probably a good idea to review where and what the Prime Meridian is before you begin. The steps are similar to showing latitude but now the lines will be vertical.
7. Once you bring the yarn to the top (North Pole) I would secure it with a thumbtack. Students should identify that spot as the North Pole. Then make any size angle. Mine is about 40 degrees in the picture. Drag the string down to the South Pole and make the same size angle and secure it with a thumbtack. Secure other “cities” along this longitude with thumbtacks as well (3rd picture). Have the students measure the angles with protractors to make sure they are equal and to identify the longitude of the city thumbtacks. For example, I chose my hemisphere to represent east of the Prime Meridian and made about a 40 degree angle. So, my thumbtack cities’ longitude would be about 40 degrees east. I would have students explore other angles. Challenge them with 180 degrees and ask them what happens there.
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