When you look out the window, does the Earth look like it's flat or like it's round? In ancient times, when sailors left shore and went too far out into the ocean, they never returned. Local residents concluded that these lost sailors had sailed off the edge of the Earth, and that the Earth must be flat.

Of course, we know now that the Earth really is round. As our understanding of the world changed, so did our need for different coordinate systems. Click on the slide show below to see how people's understanding of the world influenced their choices of coordinate systems. Click the right arrow to advance through the slides as you are ready.

Watch the movie below about Magellan's voyage around the world.

Use your notes to answer the questions below.

1. When is it useful to have a rectangular coordinate system?
2. When is it more helpful to use a spherical coordinate system?
3. Give an example of each.