十万个为什么·科学启蒙30篇（1）

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GPS设备如何知道你的精确位置？

GPS devices receive signals from at least four satellites orbiting Earth at high speed.
Each signal includes the satellite’s location and the exact time the message was sent.
The device calculates distance by measuring how long each signal took to arrive.
Using geometry called trilateration, it finds where three spheres intersect in space.
A fourth satellite helps correct timing errors and improves accuracy to within five meters.
GPS works day or night, in rain or clouds, because radio waves pass through them easily.
Your phone combines GPS with Wi-Fi and cell tower data to get even faster fixes indoors.
Maps and apps use this location data to give directions or suggest nearby places.
Military systems first developed GPS, but now civilians use it worldwide every day.
Engineers keep improving satellites so future GPS may guide self-driving cars safely.

听 → 读 → 学表达 → 懂 → 今天会说这一句 → 跟读录音 → 自己说一句。

Using geometry called trilateration, it finds where three spheres intersect in space. 利用一种名为‘三边测量’的几何方法，确定三个球体在空间中的交点。
Engineers keep improving satellites so future GPS may guide self-driving cars safely. 工程师持续升级卫星，未来GPS或将安全引导自动驾驶汽车。
The device calculates distance by measuring how long each signal took to arrive. 设备通过测量各信号到达所需时间来计算距离。

这篇中文题目最接近哪一句？ GPS设备如何知道你的精确位置？一次学校运动会的通知一份超市购物清单

课文第一句的意思更接近？ GPS设备接收至少四颗高速绕地球运行的卫星发来的信号。今天学校放假了。请把窗户打开。

这一课主要在讲什么？（看英文标题） How Do GPS Devices Know Your Exact Location? How to cook noodles A maths worksheet

Using geometry called trilateration, it finds where three spheres intersect in space.

Using geometry called trilateration, it finds where three spheres intersect in space.

第一版：录下来、回听、再听标准音。系统打分以后再加。

用今天的表达，自己说一句。

例子：Using geometry called trilateration, it finds where three spheres intersect in space.