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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
Single frequency	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.