Effect of Digital Map on Active Beidou Position System

On condition that the digital map in the controlling center provides for the user the altitude, the active Beidou Double-Star position system (for short: double-star) can determine the position of the user. This article analyzes the effect of the altitudes of digital map on the position precision, and deduces the error expressions. Many simulation results show that the effect of the altitude errors on the positioning precision meets the rules that altitude error has little effect on the east-west position error, but has large effect on the south-north position error.