为什么中国、俄罗斯和印度等国家要搭建自己的GPS系统

Why are countries such as China, Russia and India develo their own GPS system? Why wouldn’t these countries just use the US system instead of develo and maintaining their own?

为什么中国、俄罗斯和印度等国家要搭建自己的GPS系统？

以下是Quora网友的评价：

Rafsan

Because US is violating international laws and abusing satellite systems to track people and do experimentation (MINDPRISM).

因为美国违反了国际法，滥用卫星系统来跟踪民众的活动、进行实验。

Per Westling

There are several global positioning systems available so the need to create yet another one is low. I even see it as problematic to have too many systems available as the sky will become crowded.

For usage of global positioning systems, it is good to use multiple. So e.g. using both GPS (USA) and GLONASS (Russia) both makes for a more robust solution, as well as give better results as more satellites can be used.

That said, I think that countries that want to be part of the space race might consider this as a good opportunity, while for most countries it might be enough to just use exsting.

目前已经有几个可用的全球定位系统了，再建新的没什么必要。我认为定为系统太多的话汇出问题，因为空中会越来越拥挤。

对于全球定位系统的使用，最好可以获得多个系统支持。例如同时使用GPS(美国)和格洛纳斯(俄罗斯)可以提供更为强大的解决方案，并且可以使用更多的卫星，获得更好的结果。

也就是说，我认为那些想要参与太空竞赛的国家可能会认为这是一个好机会，而对大多数国家来说，只要利用现有的定位系统就足够了。

Jishnu

As the other authors already talked about China, I will now talk about India. There is a long history behind it. It goes back to the 1999 Kargil war between India and Pakistan.

其他作者谈到了中国，我想谈谈印度。印度的选择背后有着悠久的历史，可以追溯到1999年印度和巴基斯坦之间的卡吉尔战争。

When Pakistani troops took positions in Kargil in 1999, one of the first things Indian military sought was global positioning system (GPS) data for the region. The space-based navigation system maintained by the US government would have provided vital information, but the US denied it to India. A need for an indigenous satellite navigation system was felt earlier, but the Kargil experience made the nation realise its inevitability. Two decades later, NavIC, India's own GPS which has been developed to challenge the current GPS system of the West, is in the final stages of launch. It will soon be offered as an Indian counter to foreign systems currently being used by companies and others. NavIC is designed to provide accurate position information to users within the country. It will help India enter the club of select countries which have their own positioning systems. Besides America’s GPS (with 24 satellites in a constellation), Russia has its GLONASS and European Union its Galileo. Interestingly, China is also in the process of building Beidou Navigation Satellite System.

So in the last few years countries like India,China and Russia realised that they cannot always rely on USA. So they developed their on technologies.

当巴基斯坦军队1999年在卡吉尔占领阵地时，印度军方首先希望借用全球定位系统(GPS)的数据。美国政府维护的这个天基定位系统本可以提供重要信息，但美国拒绝了印度。印度早前就意识到自己应该自主研发卫星导航系统，但卡吉尔战争让印度意识到自己必须这么做。二十年后，印度自主研发的对标GPS的NavIC系统已经进入发射前的最后准备阶段。NavIC将很快成为目前主流的外国定位系统的对手。NavIC可以为国内用户提供准确的定位信息，将帮助印度跻身拥有自主定位系统的国家之列。除了美国的GPS(拥有24颗卫星)，俄罗斯有格洛纳斯系统，欧盟有伽利略系统。有意思的是，中国也在建设北斗卫星导航系统。

在过去几年里，印度、中国和俄罗斯等国家都意识到他们不能总是依赖美国，所以他们都研发了自己的系统。

Warren Shafford

almost certainly they want GPS for military reasons.

Originally it was a United States military secret. Later is was moved to civilian use.

I wouldn't trust the U.S. GPS for military reason. The United States could almost certainly see where your is. As well as you can see your own troops. So other countries need there own GPS.

几乎可以断定，他们想要自己研发GPS是为了军事的目的。

最初这是美国的军事机密，后来被转为民用。

出于军事方面的原因，我不会相信美国的GPS。你能看清自己军队位置的同时，美国应该也能把你的位置看得一清二楚。所以其他国家都需要自己的GPS才安全。

Harsh Manral

Because they believe in the famous Lines of the Poet Robert Frost— “ Two Paths diverged in a Wood and I, I chose the One Less Traveled by— And that has made all the Difference!”

因为他们相信诗人罗伯特·弗罗斯特的那句著名的诗句—“森林里分出两条路，而我选择人迹稀少的那条—这造就了一切的不同！”

Chandu Yadav

Let me explain the problems faced by the Indian army in the kargil war:

Hence the war broke between Pakistan and India until that time we are using American made GPS. As our Indian air Force is in need of using the GPS to Target the enemy post's. Mean while US has shut down it's GPS due to war and then air Force faced a lot trouble in identifying and attack the targets. But still they successed in their goal . So after the war Indian government decided to create own navigation system and it is assigned to ISRO.

Why should we depends on others?

我来解释一下印度军队在卡吉尔战争中发生过的问题：

当时巴基斯坦和印度之间爆发了战争，在此之前我们一直都使用美国的GPS。印度空军需要用GPS定位敌人的哨所。但美国因为战争关闭了GPS，印度空军在识别和攻击目标方面遇到了很多麻烦。但是他们还是成功地实现了作战目标。所以战争结束后，印度政府决定搭建自己的导航系统，并将任务分配给印度空间研究组织。

我们为什么要依赖别人？

Ramakrishnan C M

Today USA, Russia, Eu, China and India have their own GPS systems. In a short time we can expect many more nations to have their own GPS systems.

These systems have their civil and military uses ( both for defence and offence). These systems to be effective need to position four to six satellites ( geostationary or geo synchronous) over any area for greatest accuracy and ensure ‘fail safe’. Obviously countries that own and position these satellites have complete control over their access.

如今，美国、俄罗斯、欧盟、中国和印度都有了自己的GPS系统。在短期内，我们还可以期待更多的国家拥有自己的GPS系统。

这些系统可以满足民用和军事的用途(既用于防御也用于进攻)。这些系统需要配置最少4到6颗卫星(地球静止或地球同步)，才能获取最大的精度，确保“安全性”。显然，拥有和定位这些卫星的国家可以完全控制自己的使用。

The unpleasant experience that India had in 1999, during the Kargil war with Pakistan, when it requested USA for information from its GPS satellites on areas of military incursions by Pakistan lead to India develo its own GPS systems. The denial of GPS information about Pakistani military incursions into Indian territory was However not surprising, since USA has consistently flooded Pakistan with funds and armaments (which promotes aggression against India) on one pretext or another, calling Pakistan a strategic partner. This continues till date in 2019.

印度在1999年与巴基斯坦的卡吉尔战争期间要求美国提供巴基斯坦军事入侵地区的GPS卫星信息，和美国闹过不愉快，导致印度自己研发了GPS系统。但是美国拒绝提供巴基斯坦军事入侵印度领土的GPS信息并不奇怪，因为美国总是以各种借口向巴基斯坦提供资金和武器(这促成了巴基斯坦对印度的入侵)，美国把巴基斯坦视为战略伙伴。这种情况一直持续到2019年。

Even though USA has declared open access to civilian use of its GPS information which is less than the needs for military purposes, all countries are aware that even this can be withdrawn at any time. EU once considered the most reliable partner by USA is also aware of this. Russia and China being in the opposite camp to USA obviously will have their own systems.

尽管美国已经宣布开放GPS系统的民用通道，这比军事用途的需求少，但所有国家都意识到，即便如此，美国也可以随时取消使用许可。曾经被美国视为最可信赖的合作伙伴的欧盟也意识到了这一点。俄罗斯和中国与美国处于对立阵营，自然也会搭建自己的系统。

Ramanan Rv

There is so much misinformation and wrong assumptions on how GPS works.

Most people seem to think that GPS is like a DTH service that you use for watching satellite television in that you need the permission of the service provider to use it. I am tempted to say that it is more like OTA (over the air television) wherein you tune your antenna to receive signals. But it is sort of both.

对于GPS的工作原理，我看到了很多错误的信息和错误的假设。

大多数人似乎认为GPS就像你用来看卫星电视的数字高清直播电视卫星，你需要得到运营商的许可才能使用。我想说GPS更像是空中电视，你可以通过调整天线来接收信号。但确实都有点像。

Civil use GPS

If you are a ordinary user needing GPS for navigating you can use your device to receive signals from GPS satellites. Your device than deciphers the timestamps and translates it to your coordinates. However, the resolution is low. It might be good for ordinary users.

民用GPS

如果你是一个需要GPS导航的普通用户，你可以用你的设备接收来自GPS卫星的信号。你的设备会破译时间戳记并将其转换为你的坐标，但是清晰率不高，可能对普通用户来说也够用了。

Military use GPS

US Military users get a higher resolution. The signals they use for higher resolution are encrypted. I am sure you are surrounded by these encrypted signals as well but obviously the key, the type of encryption and related settings are maintained confidential.

军用GPS

美国军方用户可以获得更高的清晰度。他们的高清信号是加密的。我相信你也是被加密信号环绕着的，但显然，密钥、加密类型和相关设置都是保密信息。

Speed and altitude limits

Commercial GPS receiver units are limited to a speed ceiling of 1000 knots and altitude limit of 59,000 ft. Of course, that means you cannot use them for supersonic flights and missiles for military use.

速度和高度限制

商用GPS接收机的速度上限为1000节，高度限制为59,000英尺。当然，这也就意味着你不能将它们用于超音速飞行和军事用途的导弹发射。

Selective Availability

There used to be (or so it is said) something called Selective Availability on US GPS systems. What that means is that US would be able to turn on random errors at times of war so that enemies using the commercial signals would effectively find their units worthless. This was supposedly turned off in May 2000 by Clinton administration and all new GPS satellites are supposed to not have this feature since 2010s.

选择局限性

在美国GPS系统中曾经有一种叫做选择性局限性的东西。这意味着美国可以在战争时期开启随机误差，这样使用商业信号的敌人就会发现他们的账号毫无价值。据说克林顿政府在2000年5月关闭了这一功能，自2010年以来，所有新的GPS卫星应该都取消了这一功能。

Kargil War

Most people think that GPS is some kind of data that US shares and India asked for it and was denied. Or, as if US turned off all the signals over India.

If you have read above points related to different types of GPS and limits on commercial limits, it is more likely that India would have asked for military grade GPS receivers or to decryption keys. Obviously, India not being a US ally this would have been denied. It is as good (or bad as) asking India if it can borrow its Air Force and Navy for war.

卡吉尔战争

大多数人认为GPS是美国分享的某种数据，印度向美国提出要求，但被美国拒绝了，或者说美国似乎关闭了对印度的所有信号源。

如果你看完了上述关于不同类型的GPS和商业限制的要点，印度更有可能向美国索要的是军用级GPS接收器或解密密钥。但显然，印度并不是美国的盟友，被拒绝也很正常。这就好比某个国家向印度提出能不能借印度的空军和海军打仗一样。

Conclusion:

Nevertheless, it is clear that whatever be the mode of denial, a satellite navigation system is absolutely essential for a country that has military needs such as India and one without a reliable ally.

1.US might still have the Selective Availability on its GPS despite its claims.

2.Commercial GPS signals are not accurate enough for missiles as a small error in its initial trajectory can translate it into hundreds of kilometres at destination.

3.Even if India were to secure permission or enter into a treaty to use military grade receivers and / or decryption codes, given the political uncertainty in US, a new administration could cancel it in a whim.

结论：

很显然，无论是因为什么原因被拒绝，卫星导航系统对于像印度这样有军事需求且没有可靠盟友的国家来说都是一个绝对必要的工具。

1. 事实上美国可能仍然有GPS选择局限性的设置。

2. 商用GPS信号对导弹来说不够精确，因为轨迹上的一个小误差就能使其在到达目的地时偏离数百公里。

3. 考虑到美国政治的不确定性，即便印度获得了军用级接收器和/或解密代码的使用许可或签订了相关条约，换届后的政府也可能随时废除条约。

Rahul Gupta

(1) Most vital reason is that you cannot use GPS of US in the Military usages of country. US does not allow the GPS for military purpose.

(2) Every big country wants its own technology so that Customization according to need of country can be feasible.

(1) 最重要的原因是你不能把美国的GPS用于军事用途。美国不允许GPS用于军事目的。

(2) 每个大国都希望拥有自己的技术，这样就可以根据国家的需要进行定制。

Dk Sardana

I think GPS is owned by US.Its available mostly for civil use only. US can twist our arms anytime by switching off its use.