GPS receiver capable of calculating accurate 2DRMS

In the GPS receiver, GPS solutions are calculated by performing GPS measurement using a Kalman filter. The GPS receiver is provided with a computing system which calculates 2DRMS according to an equation:2DRMS = 2 × σH_Kalman + HDOP × σUERE    wherein, σH_Kalman represents a horizontal component of an estimate error obtained from a diagonal in an error covariance matrix calculated in a mathematical process of the Kalman filter, HDOP represents a horizontal dilution of precision, and σUERE is a user equivalent range error.