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Advantages of QZSS

In recent years more countries are developing and establishing original satellite positioning systems. However, QZSS is superior to these systems. As many countries launch positioning satellites, only Japan's QZSS is highly compatible with GPS and can be used with GPS in an integrated way; QZSS and GPS can be utilized as a single group of satellites. To put it simply, with QZSS it is like the number of GPS satellites has been increased. Because QZSS can be used in an integrated way with GPS, the number of satellites that can transmit satellite signals at the same time is increased, which makes highly precise, stable positioning possible. This also decreases the positioning errors as described.

Satellite positioning for consumer use in various countries

[Reference] The Modernization of GPS

When GPS satellites reach the end of their life span, failures can occur and the satellites are put out of service at times. Therefore, replacement GPS satellites are launched in a systematic way. When new satellites are launched, the old satellites are replaced with new-model GPS satellites with the goal of improving positioning capabilities.

The currently launched satellites are second-generation Block IIF series satellites that transmit L5 signals.

Seven second-generation Block IIA satellites - which offer poor positioning accuracy compared to the new models - are being operated, but they are being sequentially replaced with new-model satellites. The current GPS error, which is said to be 0.8 meters, will be improved to 0.4 meters by 2018, thereby drastically improving the positioning environment.

  L1C/A L1C L2C L5 Error 2014 2018 2020
Single frequency II A       One – two meters Eight satellites    
II R       0.5 meters 12 satellites 10 satellites Six satellites
Dual frequency or
multiple frequency
II RM     0.5 meters Seven satellites Seven satellites Seven satellites
II F   0.3 meters Five satellites 12 satellites 12 satellites
III 0.3 meters   Two satellites Six satellites
  Total 32 satellites Total 31 satellites Total 31 satellites
* Assuming that two satellites are launched in one year.
* "Error" is defined as an error in the satellite position transmitted by a standalone satellite.