Hundreds of years ago， travelers found their way by looking at the stars. They built towers that could be seen from far， made maps and invented the compass.
Nowadays， almost every explorer and mountain climber uses the Global Positioning System (GPS) to make their journeys safer. There are even plans to put GPS receivers on all the taxis in Beijing for the 2008 Olympics. Finding your way has never been so easy.
Technology has changed our lives： for less than 500 RMB， you can get a pocket-sized GPS gadget① that will tell you exactly where you are on Earth at any moment.
When people talk about a GPS， they usually mean a GPS receiver. The GPS is actually a set of 27 satellites network orbiting the Earth， including 24 satellites in operation and three extras.
A GPS receiver locates these satellites， records the distance to each ohter， and uses the information to calculate② the receiver’s exact position on Earth.
① gadgetn. 小机件，(小巧的)器具，小玩意儿\[C\]
② calculatev. 计算，估计，预测
找到回家的路
数百年前，旅行的人通过观察天上的星斗来识路。他们建造从远处就能看得见的灯塔，绘制地图，并发明了指南针。
现在，几乎每个探险家和登山者都使用全球定位系统（GPS）以确保旅行更安全。为了2008年奥运会，北京也计划在所有的出租车上安装GPS接收器。位置识别从来没有象现在这样容易。
技术改变了我们的生活。你只需花费不到500元钱，就能买到一个口袋儿大小的GPS部件，可以精确地告诉你某个时刻到底处于什么位置。
人们在谈到GPS时，指的通常是GPS接收器。实际上，GPS是一组由27个环地球轨道运行的卫星组成的卫星网络，其中包括24个处于运行状态的卫星和3个额外的备用卫星。
GPS接收器对这些卫星进行定位，记录下到每个卫星的距离，并使用这些信息来计算接收器所处的具体方位。