关于GPS的精度问题
GPS在刚开始定位成功时,偏差很大,过一段时间,会慢慢较准。我一直的理解是刚开始参与定位的卫星少,后来多了以后才更精准的。
偶然发现有别的因素。
1、先列官方最简单直接的说明,Selective Availability,摘录如下:http://www.gps.gov/systems/gps/modernization/sa/
Selective Availability
chart GPS accuracy errors before and after deactivation of SA (VIEW MORE DATA)
Selective Availability (SA) was an intentional degradation of public GPS signals implemented for national security reasons.
In May 2000, at the direction of President Bill Clinton, the U.S government discontinued its use of Selective Availability in order to make GPS more responsive to civil and commercial users worldwide.
The United States has no intent to ever use Selective Availability again.
In September 2007, the U.S. government announced its decision to procure the future generation of GPS satellites, known as GPS III, without the SA feature. Doing this will make the policy decision of 2000 permanent and eliminate a source of uncertainty in GPS performance that had been of concern to civil GPS users worldwide.