Abstract: The closed expression form of the maximum carrier phase tracking error caused by multipath effect is derived in this paper based on multipath signal characteristics and GPS receiver work mechanism. The conclusions are drawn: When the code tracking error of a direct signal is no more than one chip and the code ranging multipath error is the least, a maximum carrier phase error occurs and its value is a quarter cycle. When the code tracking error of a direct signal is equal to or more than one code chip, the multipath signal is being tracked and false detection occurs. Because the maximum carrier phase multipath error is much less than the maximum code ranging multipath error, carrier phase differential technology causes extensive attention in GPS application, but it is still a main obstacle in precise measuring.

Key words: global positioning system, multipat h effect, carr ier pha se