手机中的 GPS 究竟是如何工作的? [英] How does GPS in a mobile phone work exactly?
问题描述
我假设它没有连接到任何东西(除了我猜的卫星)，对吗?或者它确实并且有某种收费?
I assume it doesn't connect to anything (other than the satelite I guess), is this right? Or it does and has some kind of charge?
推荐答案
GPS 是美国军方运行的全球定位系统，可免费用于民用，但现实是我们用税金支付它.
GPS, the Global Positioning System run by the United States Military, is free for civilian use, though the reality is that we're paying for it with tax dollars.
但是，手机上的 GPS 有点模糊.一般来说，打开手机中的 GPS 不会花费您任何费用，但是当您获得位置时，通常会涉及手机公司，以便在没有信号的情况下快速获得位置，以及在何时获得位置卫星是不可见的(因为即使卫星在紧急 911 中不可见，政府也不需要修复).它占用了一些蜂窝带宽.这也意味着对于没有常规 GPS 接收器的手机，如果您没有手机服务，则根本无法使用 GPS.
However, GPS on cell phones is a bit more murky. In general, it won't cost you anything to turn on the GPS in your cell phone, but when you get a location it usually involves the cell phone company in order to get it quickly with little signal, as well as get a location when the satellites aren't visible (since the gov't requires a fix even if the satellites aren't visible for emergency 911 purposes). It uses up some cellular bandwidth. This also means that for phones without a regular GPS receiver, you cannot use the GPS at all if you don't have cell phone service.
因此，大多数手机公司都会关闭手机中的 GPS，但紧急呼叫和他们向您出售的服务(例如路线)除外.
For this reason most cell phone companies have the GPS in the phone turned off except for emergency calls and for services they sell you (such as directions).
这种特殊类型的 GPS 称为辅助 GPS (AGPS)，并且使用了多个级别的辅助.
This particular kind of GPS is called assisted GPS (AGPS), and there are several levels of assistance used.
普通的 GPS 接收器会收听特定频率的无线电信号.卫星以此频率发送时间编码信息.每颗卫星都有一个原子钟，并发送当前的准确时间.
A normal GPS receiver listens to a particular frequency for radio signals. Satellites send time coded messages at this frequency. Each satellite has an atomic clock, and sends the current exact time as well.
GPS 接收器确定它可以听到哪些卫星，然后开始收集这些信息.这些消息包括时间、当前卫星位置和其他一些信息.消息流很慢——这是为了节省电力，也是因为所有卫星都以相同的频率传输，如果它们运行缓慢，它们更容易被识别出来.因此，以及正常运行所需的信息量，在常规 GPS 上获取位置可能需要 30-60 秒.
The GPS receiver figures out which satellites it can hear, and then starts gathering those messages. The messages include time, current satellite positions, and a few other bits of information. The message stream is slow - this is to save power, and also because all the satellites transmit on the same frequency and they're easier to pick out if they go slow. Because of this, and the amount of information needed to operate well, it can take 30-60 seconds to get a location on a regular GPS.
当它知道至少 3 颗卫星的位置和时间码时，GPS 接收器可以假定它位于地球表面并获得良好的读数.如果您不在地面上并且还需要高度，则需要 4 颗卫星.
When it knows the position and time code of at least 3 satellites, a GPS receiver can assume it's on the earth's surface and get a good reading. 4 satellites are needed if you aren't on the ground and you want altitude as well.
正如您在上面看到的，使用普通 GPS 可能需要很长时间才能获得定位.有一些方法可以加快速度，但除非你一直随身携带原子钟，或者一直打开 GPS，否则在你得到一个之前总会有 5-60 秒的延迟.位置.
As you saw above, it can take a long time to get a position fix with a normal GPS. There are ways to speed this up, but unless you're carrying an atomic clock with you all the time, or leave the GPS on all the time, then there's always going to be a delay of between 5-60 seconds before you get a location.
为了节省成本，大多数手机与蜂窝组件共享 GPS 接收器组件，您无法同时获得定位和通话.人们不喜欢这样(尤其是在紧急情况下)，因此最低形式的 GPS 会执行以下操作:
In order to save cost, most cell phones share the GPS receiver components with the cellular components, and you can't get a fix and talk at the same time. People don't like that (especially when there's an emergency) so the lowest form of GPS does the following:
- 从手机公司获取一些信息以馈送到 GPS 接收器 - 其中一些是基于蜂窝塔可以听到"您的手机的大致定位信息，因此此时他们已经将您的位置通过电话告知城市内块左右.
- 从蜂窝网络切换到 GPS 接收器 0.1 秒(或一些小的、实际上不明显的时间段)并收集原始 GPS 数据(手机上不进行处理).
- 切换回电话模式，并将原始数据发送给电话公司
- 电话公司处理该数据(充当离线 GPS 接收器)并将位置发送回您的手机.
这在手机设计上节省了大量资金，但它对蜂窝带宽造成了沉重的负担，并且随着大量请求的到来，它需要大量快速服务器.尽管如此，总体而言，实施起来可能更便宜、更快捷.然而，由于这种负载，他们不愿意在这些手机上发布基于 GPS 的功能 - 因此您不会在此处看到转弯导航.
This saves a lot of money on the phone design, but it has a heavy load on cellular bandwidth, and with a lot of requests coming it requires a lot of fast servers. Still, overall it can be cheaper and faster to implement. They are reluctant, however, to release GPS based features on these phones due to this load - so you won't see turn by turn navigation here.
最近的设计包括一个完整的 GPS 芯片.他们仍然从电话公司获取数据——例如基于塔定位的当前位置和当前卫星位置——这提供了不到 1 秒的定位时间.该信息只需要一次，并且 GPS 可以用很少的电量跟踪之后的所有内容.如果蜂窝网络不可用，那么他们仍然可以在一段时间后得到修复.如果 GPS 卫星对接收器不可见，那么它们仍然可以从蜂窝塔获得粗略的修复.
More recent designs include a full GPS chip. They still get data from the phone company - such as current location based on tower positioning, and current satellite locations - this provides sub 1 second fix times. This information is only needed once, and the GPS can keep track of everything after that with very little power. If the cellular network is unavailable, then they can still get a fix after awhile. If the GPS satellites aren't visible to the receiver, then they can still get a rough fix from the cellular towers.
但要完全回答您的问题 - 电话公司允许它免费，而且到目前为止他们根本不收费.我怀疑这在未来会改变.在带有完整 GPS 接收器的高端手机中，您甚至可以加载自己的软件并访问它，例如在摩托罗拉 iDen 手机上使用 mologogo - J2ME 开发套件是免费的，而且手机只需 40 美元(预付费手机5 美元的信用).无限上网每月大约 10 美元，因此只需 40 美元开始，每月 10 美元，您就可以获得一个网络跟踪系统.(价格约为 2008 年 8 月)
But to completely answer your question - it's as free as the phone company lets it be, and so far they do not charge for it at all. I doubt that's going to change in the future. In the higher end phones with a full GPS receiver you may even be able to load your own software and access it, such as with mologogo on a motorola iDen phone - the J2ME development kit is free, and the phone is only $40 (prepaid phone with $5 credit). Unlimited internet is about $10 a month, so for $40 to start and $10 a month you can get an internet tracking system. (Prices circa August 2008)
从现在开始，它只会变得更便宜，功能更齐全......
It's only going to get cheaper and more full featured from here on out...
回复:谷歌地图等
是的，Google 地图和所有其他手机地图系统在使用过程中的不同时间都需要某种数据连接.例如，当您向一个方向移动足够远时，它会从其服务器请求新的图块.您的普通手机没有足够的存储空间来保存美国地图，也没有足够的处理器能力来很好地渲染它.如果您想将存储空间与地图一起使用，iPhone 将能够做到这一点，但鉴于大多数 iPhone 都有全时无限数据计划，大多数用户宁愿将该空间用于其他事情.
Yes, Google maps and all other cell phone mapping systems require a data connection of some sort at varying times during usage. When you move far enough in one direction, for instance, it'll request new tiles from its server. Your average phone doesn't have enough storage to hold a map of the US, nor the processor power to render it nicely. iPhone would be able to if you wanted to use the storage space up with maps, but given that most iPhones have a full time unlimited data plan most users would rather use that space for other things.
这篇关于手机中的 GPS 究竟是如何工作的?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
