Grade 9 Unit 4 Topic 1 Section D

Where Are We?
Where are we? That was a big question when we first explored our world long ago. The early explorers found that the stars in the sky were good guiding marks. Using the stars. they could find out where they were and in which direction they were going. This method worked well at night as long as the weather was good and the stars could be seen. But it didn’t work so well during the rest of the time. That was a problem.

Today, the problem has been solved by the Global Positioning System(GPS). It is like a man-made star. We can use it at any time, in any place and in any weather to find out our position. It can also be used to study the shape of the earth. The GPS is a great invention that helps us explore our planet and discover where we are.

如有需要请联系QQ:695125000 » Grade 9 Unit 4 Topic 1 Section D