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.
|Single frequency||II A||◎||One – two meters||Eight satellites|
|II R||◎||0.5 meters||12 satellites||10 satellites||Six satellites|
|Dual frequency or
|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|
* "Error" is defined as an error in the satellite position transmitted by a standalone satellite.