手机中的GPS如何工作？ [英] How does GPS in a mobile phone work exactly?

问题描述

我认为它没有连接任何东西（除了我猜测的卫星），这是正确的吗？或者它有，并有一些收费？

解决方案

由美国军队运行的全球定位系统GPS是免费的尽管现实是我们用税收支付了它。

但是，手机上的GPS更加模糊。一般来说，在您的手机上打开GPS并不会花费任何费用，但是当您获得一个位置时，它通常会涉及手机公司，以便在几乎没有信号的情况下快速获取，以及在获取位置时卫星不可见（因为即使卫星因紧急911目的而不可见，政府也需要修理）。它消耗了一些蜂窝带宽。这也意味着，对于没有普通GPS接收器的手机，如果您没有手机服务，则根本无法使用GPS。

由于这个原因，大多数手机公司已经关闭手机中的GPS，除了紧急呼叫和他们向您出售的服务（例如路线指示）。 b
$ b

这种特殊类型的GPS称为辅助GPS AGPS），并且使用了几个级别的援助。

GPS

一个普通的GPS接收机监听无线电信号的特定频率。卫星以这个频率发送时间编码信息。每个卫星都有一个原子钟，并发送当前的准确时间。

GPS接收器会计算出它可以听到的卫星，然后开始收集这些信息。这些消息包括时间，当前的卫星位置和其他一些信息。信息流速度很慢 - 这是为了节省电力，也是因为所有的卫星都以相同的频率传输，而且如果速度较慢，他们更容易选择。正因为如此，以及运行良好所需的信息量，可能需要30-60秒才能在常规GPS上获得位置。

当它知道位置和至少3颗卫星的时间码，GPS接收机可以假设它在地球表面并获得良好的读数。如果您不在地面上，并且您还想要高度，则需要4颗卫星。

AGPS

正如您在上面看到的，使用普通的GPS可能需要很长时间才能找到位置。有许多方法可以加快速度，但除非您始终携带原子钟，或始终保持GPS不变，否则总是会有5-60秒的延迟，然后才能得到位置。

为了节约成本，大多数手机与蜂窝组件共享GPS接收器组件，并且无法同时获得修复和通话。人们不喜欢这种情况（特别是在紧急情况下），所以GPS的最低格式会执行以下操作：

1. 手机公司提供给GPS接收器 - 其中一些是基于蜂窝塔可以听到你的手机的总定位信息，所以到目前为止，他们已经将你的位置打到了城市街区等等。


2. 从手机切换到GPS接收机0.1秒（或者一些小的，几乎不可能的时间段）并收集原始的GPS数据（手机上不处理）。
   
3. 切换回电话模式，并将原始数据发送到电话公司
   
4. 电话公司处理该数据（用作离线GPS接收器）并将位置发回给您手机。
   

这为手机设计节省了大量资金，但它对手机带宽负担很重，而且很多的要求，它需要很多快速的服务器。不过，总体来说，实施起来可能更便宜，速度更快。然而，他们不愿意在这些手机上发布基于GPS的功能 - 因此您不会在这里看到轮到导航。

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得数据 - 例如基于塔定位的当前位置和当前的卫星位置 - 这提供了小于1秒的修复时间。这个信息只需要一次，GPS可以在几乎没有电力的情况下跟踪所有事情。如果蜂窝网络不可用，那么他们在一段时间后仍然可以修复。如果GPS卫星对接收器不可见，那么它们仍然可以从蜂窝塔楼中大致修复。

但要完全回答您的问题 - 它是免费的正如电话公司所说的那样，到目前为止，他们根本没有收费。我怀疑这将在未来发生变化。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，例如摩托罗拉iDen手机上的mologogo - J2ME开发套件是免费的，手机只有40美元（预付费电话5美元）。无限上网费用大约是每月10美元，因此只需40美元即可启动，每月10美元即可获得互联网跟踪系统。 （价格大约在2008年8月）

从这里开始，它只会变得更便宜，更全面... ...

Google地图和其他手机地图系统在使用过程中需要不同时间的某种数据连接。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。您的平均手机没有足够的存储空间来放置美国地图，也没有足够的处理器来渲染它。如果您希望将存储空间与地图一起使用，iPhone将能够实现，但鉴于大多数iPhone拥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。

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?

解决方案

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.

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.

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).

This particular kind of GPS is called assisted GPS (AGPS), and there are several levels of assistance used.

GPS

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.

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.

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.

AGPS

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.

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:

1. Get some information from the cell phone company to feed to the GPS receiver - some of this is gross positioning information based on what cellular towers can 'hear' your phone, so by this time they already phone your location to within a city block or so.
2. Switch from cellular to GPS receiver for 0.1 second (or some small, practically unoticable period of time) and collect the raw GPS data (no processing on the phone).
3. Switch back to the phone mode, and send the raw data to the phone company
4. The phone company processes that data (acts as an offline GPS receiver) and send the location back to your phone.

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.

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.

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)

It's only going to get cheaper and more full featured from here on out...

Re: Google maps and such

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如何工作？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！