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出人意料的GPS用法

Unexpected Ways Scientists Use GPS

Thanks to Brilliant for supporting this episode of SciShow.
感谢Brilliant对本集《科学秀》的支持
Go to Brilliant.org/SciShow to check out their interactive courses
可进入Brilliant.org/SciShow查看互动课程
and to get 20% off an annual premium subscription!
并享受会员年费八折优惠!
[♩ INTRO ]
[开场音乐]
If you’re a regular driver or have ever looked at your phone for directions,
如果你经常开车 或是曾用过手机导航
you are probably familiar with how useful GPS can be in everyday life.
那你应该知道GPS在生活中非常有用
But GPS can also be really useful for scientists,
而对科学家来说 GPS也大有用处
and not just in ways you might expect
除了追踪动物等常规用途
like by helping them track animals.
它还有很多意想不到的用途
Scientists can also use GPS to help predict how bad a tsunami might be
GPS可以帮科学家预测海啸的级别和破坏力
to warn people about flash floods,
进而向人们发出洪灾警报
or to measure how dry a forest gets during a drought.
GPS还可以测算旱灾时森林的干旱程度
All by taking advantage of two very basic ideas.
这些都是利用了两个基本思路
For context, GPS, or the Global Positioning System, works
背景知识:GPS(全球定位系统)的运作
thanks to 31 satellites orbiting about 20,000 km above earth.
全靠31颗卫星 绕行在离地2万公里的轨道上
All of us being served by 31 satellites!
全世界的人只靠31个卫星来服务!
Those satellites transmit signals to the ground,
那些卫星把讯号传输到地面
and then receivers in phones, cars, or other devices can pick them up
然后手机 汽车或其他设备里的接收器就能
and use them to calculate how far away the satellite is.
接收并通过讯号算出到卫星的距离
Then, by triangulating with four or more satellites,
接收器与至少四颗卫星进行三角测距
that receiver can figure out its exact position on earth.
然后算出它在地球上的准确位置
Now, there is some nuance.
不过 不同设备会有细微差别
For instance, scientific receivers use a slightly tweaked version of this process
例如 科研接收器在此基础上进行了微调
to pinpoint their location down to a couple of millimeters
因此定位误差只有几毫米
—compared to the 1 to 10 meters phones can do.
相比之下 手机的定位误差在1到10米
But that’s basically it! And if you get creative,
但只有这点差别 而且如果你更有创造力
this technology can help you measure a lot more than location.
那这项技术能帮你测量的远不止位置
Like, because GPS receivers are so good at calculating where they are,
比如 因为GPS接收器能精确定位
they’re also good at measuring how the ground moves
所以它们也能测量地表运动
—and by extension, how strong earthquakes are.
广义上来说 也就是测量地震强度
Traditionally, we use seismometers for this;
我们一般用地震仪来完成这项工作
these are devices that measure how much a suspended weight bounces around during an earthquake.
地震仪会记录地震时悬锤的振动情况
But seismometers can get overwhelmed during really strong quakes, above magnitude eight or so.
但八级以上大地震就超出地震仪的测量上限了
And that’s especially a problem when it comes to predicting tsunamis.
而这一点在预测海啸时 尤其成问题
A tsunami is a giant wave or series of waves
海啸是因海水猛烈移动
caused by water suddenly being displaced,
而形成的一阵或几阵巨浪
like by an undersea earthquake.
海底地震会造成海啸
So, by measuring how strong a quake is,
所以 通过测量海底地震的强度
scientists can predict when the resulting tsunami will reach land.
科学家就能预测随之而来的海啸到达陆地的时间
Except, if a seismometer gets overwhelmed,
可是 如果地震仪爆表了
scientists might need to wait for instruments farther from the quake
科学家就可能要等离震源很远的其它仪器
to give them usable or accurate data.
传来有用的或精确的数据
And the longer the delay, the less time there is to evacuate people.
数据耽搁的越久 疏散人群的时间就越少
So, researchers have been investigating using scientific GPS receivers
为此 科研人员正在研究用GPS接收器预测海啸
to predict tsunamis instead, adding that capability to their oldschool seismometers.
并将这种功能整合到传统地震仪上
And it seems pretty promising!
这似乎很有前景!
In one paper, a team found that
在一篇论文中 科研团队发现
the magnitude of the 2004 Sumatra earthquake in Indonesia
2004年印尼苏门答腊地震的震级
could have been calculated accurately in only 15 minutes with GPS.
本可以用GPS在短短15分钟内准确计算出来
Hours faster than the system they were using.
比当时他们用的方法快几个小时
This general idea of using GPS to measure ground motion
GPS检测地表移动的大体思路
also allows scientists to measure the amount of water on the ground.
也能帮助科学家测量地表水量
When there’s a lot of water in an area, like because of a high tide or a heavy snowpack,
涨潮 积雪等都会导致某个区域水量过多
it can push the earth downwards.
这会导致地面下沉
Now it’s too small for us to notice,
我们无法察觉到这种细微变化
but a GPS unit can pick it up, no problem.
GPS组件却能毫不费力的检测到
And by measuring these tiny depressions,
科学家可以通过测量这些微小的下沉
scientists can estimate things like how much water is in a mountain range,
估算出山脉中的含水量等信息
which could be important for studying climate change
这对于研究气候变化和预测旱灾等级
or predicting how bad a drought might be.
可能有重要意义
That said, there’s another way scientists can study both tsunamis
除此以外 科学家还有另外一种通过GPS
and climate change with GPS.
研究海啸和气候变化的方式
And it is completely different.
而且是一种截然不同的方式
Instead of watching the ground move, they study interference in GPS signals.
他们研究GPS信号受到的干扰 而不是观察地表运动
Like, take tsunamis.
以海啸为例
As a tsunami travels, it raises the surface of the ocean.
海啸移动的过程中会抬升海面
In shallow water, that’s obvious — but at sea, where the ocean is deep,
这在浅水区很明显 但在水深的海域
the waves can be less than a meter high and hard to detect.
浪的高度有时不到1米 很难被探测到
Except, the wave’s motion is also transmitted to the air above the water,
但海浪运动产生的波会传播到海上的空气中
generating another set of long, strong waves in the atmosphere.
并在大气中产生另一组强烈的长波
These waves continue traveling upward
这些波继续向上传播
and eventually travel through a region called the ionosphere
最终在距海平面80公里的地方
that starts about 80 kilometers up.
进入一个名为“电离层”的区域
In this region, radiation from the Sun is so strong,
在这个区域 太阳辐射很强
it strips the electrons off molecules,
强到足以使分子电离 产生电子
creating a region of electrically charged air.
从而形成一个电离的大气区域
And when the tsunami-generated waves reach that area,
当海啸产生的波到达这个区域时
they jostle all those charged particles back and forth.
海啸波会来回推挤这些带电粒子
The key thing is, GPS satellites orbit through the ionosphere,
关键是 GPS卫星绕地运行时会穿过电离层
so they have to transmit their signals through that region.
所以卫星发射的讯号也会穿过电离层
And all the jostling caused by tsunamis creates interference in those signals.
海啸波推挤带电粒子时会干扰讯号
So, by looking for that interference,
因此 通过寻找讯号干扰
GPS units might be able to detect tsunamis while they are still out at sea,
GPS装置能探测到还在远海区域移动的海啸
just by looking at the air.
仅仅靠在空中找讯号就行了
Again, that means faster, more accurate warnings,
这意味着预警将会更快速 更准确
and more time to get people to safety.
并且有更充裕的时间疏散人群到安全地带
Similarly, this general technique also allows GPS
利用类似原理 通过这种技术
to predict events like flash floods.
GPS还能用来预测山洪暴发
In this case, changes in the amount of water vapor in the air
具体原理是 水蒸气能吸收和散射讯号能量
can muck with GPS signals in measurable ways,
所以空气中的水蒸气含量变化会干扰GPS讯号
since water droplets can absorb and scatter the signal’s energy.
这样我们就能通过测量讯号变化预测山洪爆发
In fact, this principle is already in use in Southern California,
事实上这一原理已经在南加州得到应用
where local weather forecasters use GPS signals
当地的气象预报员利用GPS讯号
to more accurately predict flash flood warnings.
来更准确地发出山洪爆发警报
In one area, this let them update predictions every halfhour,
在某个区域 他们可以每半小时就更新一次山洪预报
instead of just twice a day, which had been the norm for weather balloons.
而如果用气象气球来预报 一天只能更新两次
Finally, measuring interference can even tell scientists
最后 通过测量讯号干扰 科学家甚至
how much water is in nearby plants.
可以测出周围植物的含水量
Just like water vapor, water in plants can absorb and
跟水蒸气一样 植物中的水也可以
scatter the energy of incoming GPS signals.
吸收和散射GPS讯号中的能量
And scientists have put this to the test.
科学家们已经进行过测试
They were actually able to measure how dry the plants were
2012-2014年加利福尼亚州旱灾期间
at some GPS sites during the 2012 to 2014 drought in California.
他们已经能测出GPS讯号点附近植物的含水量了
This kind of data could be useful for scientists
有些科学家想研究气象事件和气候变化
looking to understand how weather events or climate change
对某些特定区域里的植物的影响
may be affecting what’s growing in a given region
他们能用这些GPS讯号数据进行研究
without having to actually drive or hike out there,
而不用真的开车或者跋山涉水到那里
helping us map out our changing world more easily.
这样我们能更轻松的了解不断变化的世界
In each of these examples, scientists have found ways to tweak an existing technology
每个例子中 科学家都通过调整现有技术
to learn even more about the world.
来更进一步地了解世界
And not only that, but they’ve made a lot of progress by looking at GPS interference.
不仅如此 通过关注GPS干扰 他们已经获得了不少成果
They have taken what’s usually considered a problem and turned it to our advantage.
他们把通常被视为问题的讯号干扰转变为有用的技术
And you thought GPS was just for getting you to the nearest coffee place.
而你以为GPS只是帮你找最近咖啡店的
I don’t know about you, but I’m still stuck at the
不知道你怎么想 但我还沉浸在
“tsunamis can be felt from space” thing.
对“在太空感知海啸”的感叹里
If you would like to learn more about how that’s even possible,
如果想学习更多相关知识
you might like Brilliant’s course Waves and Light,
可以看看Brilliant的“波与光”课程
where you’ll learn about the waves involved in everything
在课程里 你将会学习到各种“波”
from earthquakes to noisecanceling headphones.
从地震波到降噪耳机的波
Brilliant is an online learning platform with tons of courses
Brilliant是一个线上学习平台 拥有海量课程
that will help you learn more about
帮助你学习更多知识
science, engineering, math, and computer science.
包括科学 工程学 数学和计算机科学
Courses are available offline using their iOS and Android app.
课程可以在ios和安卓APP中离线学习
So if you’re traveling or have a spotty internet connection,
所以如果你在路上或网络不稳定
you’ll still be able to keep learning.
仍然可以继续学习
And you can get started at brilliant.org/scishow,
进入brilliant.org/scishow看看吧
where you can also get 20% off an annual premium subscription to Brilliant.
还可以享受Brilliant会员年费八折优惠哦
And by checking them out, you’re also helping to support us, so thanks.
浏览Brilliant平台也是对我们的支持 谢谢
[ OUTRO ♩ ]
[片尾音乐]

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视频概述

GPS除了能给你指路,还能帮助科学家预测地震、海啸甚至测量植物的含水量

听录译者

收集自网络

翻译译者

AG

审核员

审核员RYAN

视频来源

https://www.youtube.com/watch?v=ObRYNKXwzrs

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