，北斗，伽利略， GLONASS ）和两个区域性导航系统（ IRNSS ， QZSS ）。 There are currently four major global navigation systems ( GPS , Beidou, Galileo, GLONASS ) and two regional navigation systems ( IRNSS , QZSS ) in the world.
Let's briefly introduce the main indicators of the evaluation navigation system:
隶属于美国空军，我国北斗隶属于解放军某部，俄罗斯GLONASS也隶属军方。 Military value: The main purpose of the navigation system is to serve the military, which is consistent in all countries in the world. GPS belongs to the United States Air Force, China's Beidou belongs to a certain part of the PLA, and Russia's GLONASS also belongs to the military.
Civil value: At present, all navigation systems are open to low-level signals for civilian use. Only mobile phones and vehicle navigation that we use are important. One important thing is that civilian use can make money, so the ability to make money and commercialize is an important indicator.
厘米精度的肯定比1米的好，能1分钟定位的肯定比1小时的好，独立的肯定比依赖其他卫星系统的好，这是没有疑问的。 Practicality: Globally better than regional, 1 cm accuracy is better than 1 meter, 1 minute positioning is better than 1 hour, independent is better than relying on other satellite systems, there is no doubt of.
Stability: Several systems are in a competitive state, so it is necessary to maintain the stability of the existing state, and frequently launch satellite supplements (after all, satellite constellations of dozens of large satellites), and due to competition and demand must be updated.
多年的成熟系统，全球覆盖； There is no doubt that mature systems have been developed for more than 30 years, with global coverage;
； The military value is extremely high. Almost all weapons in the United States today, from spy satellites to bombs thrown by aircraft, are GPS ;
The fourth largest space project in the history of mankind, behind the International Space Station, the Space Shuttle, and the Apollo moon landing, with advanced technology and extremely high military accuracy;
颗，比理论值24还要多； The satellites are stable and supplemented, and remain at 32 for a long time, which is more than the theoretical value of 24 ;
Updated to the third generation, currently the world's most advanced navigation satellite;
兼容 It is important that the civilian market is basically a monopoly in the world, and its commercial value far exceeds the military investment, creating a world-class 100 billion-level navigation market. Basically, all the later systems cannot compete, because the status of latecomers entering the commercial market is generally "Dual mode" mode: certain system + GPS compatible
年实现全球高精度稳定定位的覆盖。 Stable positioning has covered the Asia-Pacific region, and it is officially announced that 2020 will achieve global high-precision and stable positioning coverage. 地球静止轨道+倾斜同步轨道设计，在亚太地区的精度更高，与GPS同一水准，相当于全球+区域增强； Due to the unique design of the middle orbit + geostationary orbit and inclined synchronous orbit, the accuracy in the Asia-Pacific region is higher, the same level as GPS , equivalent to global + regional enhancement;
的依赖，战略级地位； The military value is extremely high, and it has got rid of the dependence of Chinese weapon guidance on GPS and has a strategic position;
短报文功能，技术上与GPS各有千秋，我这个领域近些年关于卫星导航的新文章感觉三分之一到一半都是关于中国北斗的； Three-frequency signal + short message function, technically have their own advantages with GPS , in my field in recent years, new articles on satellite navigation feel that one-third to half are about China's Beidou;
颗工作状态的卫星，跨越三代卫星，且中国财力强，目前进展稳定，卫星系统妥妥的维持得很好； There are 21 satellites in working status, spanning three generations of satellites, and China has strong financial resources. At present, the progress is stable and the satellite system is properly maintained.
The shortcoming is that it is difficult to commercialize, it is difficult to promote to other countries (but it can go to the Belt and Road), and it has limited prospects in Europe, the United States and Russia. But the advantage is that China's size is very large, relying on the government to push the domestic market is enough to become the world's second.
高精度+全球覆盖，技术上三家各有千秋； The former Beidou "teacher" has three frequencies + high precision + global coverage, and each of them has its own advantages in technology;
The European military is basically the American European Theater, so the military value is very small, so Galileo is the only one that started as a "civilian" system;
年后终于重新开始发卫星了，现在有了18颗，要陆续补到30颗，全球覆盖； After being delayed for 10 years, the satellites finally started to be launched again. Now there are 18 satellites, and they have to be supplemented to 30 in succession, with global coverage;
很成熟，欧洲跟美国关系好，既然能便宜买为啥自己造，同样的道理也出现在它开始商业化的时候，也没有欧盟力推，根本无法撼动GPS的地位；不过考虑到他成熟后欧美的接收机都可能变成GPS+Galileo双模，还是能捞到不少钱的，不一定低于中国。 Commercialization is also difficult. GPS is very mature. Europe has a good relationship with the United States. Since it can be bought cheaply, it is made by itself. The same reason also appeared when it began commercialization. Without the EU's push, it could not shake the status of GPS . However, considering that his receivers in Europe and the United States may become GPS + Galileo dual-mode after he matures, he can still earn a lot of money, not necessarily lower than China.
Strong anti-interference and deception, and the unique orbital design makes the application value in high latitudes high;
The military value is extremely high, the Soviet Union is alive, and the Russian government is spending a lot of money on projects today, and it can see its status;
颗，俄罗斯如果经济进一步衰落，或者换一个没有普京这么强势的总统，未来难说（普京是GLONASS脑残粉啊，撸起袖子支持）； The number of satellites is maintained at 24 in theory. If Russia's economy further declines, or if it is replaced by a president that is not as strong as Putin, it will be difficult to say in the future (Putin is a GLONASS brain residual powder, and his sleeves are supported);
Compatibility with other systems is difficult, and the population in high latitudes is too small. It is difficult to play with Europe and the United States. After the other systems are up, there is almost no advantage in competition and there is almost no commercial potential.
5. India's Regional Navigation System IRNSS
的区域增强系统，后来印巴冲突被美国关掉一次GPS服务痛定思痛，现在IRNSS是一个独立的，但依然是一个区域增强系统，只能围着印度这一片用。 There used to be an area enhancement system that relied on GPS . Later, the India-Pakistan conflict was shut down by the United States once. GPS services were painful. Now IRNSS is an independent, but still an area enhancement system, which can only be used around India.
6. Japan's QZSS
Now only three stars are also regional systems. The more important one is:
区域增强系统，针对日本附近。 This is a standard GPS area augmentation system, targeted near Japan. 服务、加强GPS系统在日本地区应用的系统，发的信号都和GPS一样； Or to make it simpler, this is a system that relies on GPS services and strengthens the application of GPS systems in Japan. The signals sent are the same as GPS ;
In other words: if the United States turns off the signal, it will not be used.