GPS receivers are categorized into different types by its purposes, frequency and channel.A. By Purposes1. Aviation GPS receiver: It is mainly used in aviation of moving carriers. It tells locations and speed of the moving carrier in real time. Measured psychologically with C/A number, so its single positioning is less precise which is about +-25 MM. If affected by SA, the differences can be +-100 MM. The kind of GPS receivers is less expensive and widely used in various industries.2. Ground GPS receiver: It is mainly used in precise ground and engineering measurement. It uses the value of carrier phase to measure the relative position, so the result is precise. The receiver is built complicatedly, so the price is highers.3. Time transfer GPS receiver: It transfer time by highly precise satellite. It is usually used in the the observatory and wireless communication.B. By Frequency1. Single-channel GPS receiver: It only receives signal of L1 carrier wave and positions by value of carrier phase. It can’t eliminate the affect of ionosphere delay, so it is only applicable for precision position of ultra short base line less than 15 KM.2. Double-channel GPS receiver: It can receive carrier signals of both L1 and L2. With its differences to ionosphere delays, the delay of electromagnetic wave signal caused by ionosphere can be eliminated. Therefore, it can be used in precision position for thousands of kilometers.C. By Channels: GPS receivers can receives signals transmitted from multiple GPS satellites at the same time. It uses antenna singal channel to separate the signals received and track, handle and measure individual satellite. The channels are divided into multi-channel receiver, serial channel receiver and multi-channel receiver.