Talking about directions

词汇语法及实用表达

take a highway走高速take exit 29出口29
get on/off the highway上下高速
reach our destination到达目的地

对话场景

文化拓展

How does GPS work?

GPS工作原理

We take for granted how easy it is to get around these days. Here’s an explanation of how GPS navigation works — so you can appreciate it a little more the next time it gets you where you need to be.

我们现在认为想去哪就去哪是理所当然的。这里我们要解释一下GPS导航的工作原理，听完之后，下次再使用GPS导航去想去的地方时，你也许会对GPS有一点点感激之情。

GPS was originally intended for use by the U.S. military to deploy weapons. But in 2000, President Bill Clinton opened the GPS system to the world at large, citing its global utility. The system cost $10-12 billion to build, and the yearly costs of upkeep were estimated at $400 million.

GPS最开始用于协助美国军方部署武器。到了2000年，比利·克林顿总统将GPS向全球公开，称其对全球都有实用价值。GPS搭建成本达100亿元至120亿美元，每年维护成本估计达到4亿美元。

Your GPS device can tell you your precise location in a process called trilateration. It communicates with three satellites in sight — using high-frequency, low-power radio signals that travel at the speed of light — and then calculates the distance between those satellites and your device.

GPS设备可以告诉使用者的准确位置，其过程称为三角测量法。GPS设备使用光速传播的高频低功率无线电信号，与视线中的三个卫星通信，然后计算这些卫星与使用者设备的距离。

Since the satellites have a fixed orbital pattern and are synced with atomic clocks from the U.S. Naval Observatory, this process tends to yield an accurate location reading. But to improve accuracy, GPS devices typically seek data from four or more satellites, especially for determining altitude.

因为卫星有固定的运动轨迹，时间与美国海军天文台的原子钟同步，所以通过三角测量，就可以生成准确的位置读数。为了提高定位精确度，特别是确定海拔时，GPS通常会获取四颗及以上的卫星的数据。

Source: Mashable, “How does GPS know where you are?”

思维发散

????未完待续…