摘要
千万里，动物大迁徙。它们穿越大陆,飞越海洋,年复一年。漫漫长途，它们是怎样判断方位的呢？
Have you ever run into trouble finding a location？ Fortunately, we humans have a wide variety of marvelous technology at our fingertips to make it easy. Today, we can use a smartphone （智能手机） that communicates with Global Positioning System （GPS） satellites circling Earth to tell us exactly where we are and exactly how to get to where we want to be.
