While GPS receivers may be designed for a variety of functions aviation, marine navigation, land navigation, etc. Sequential receivers are the least expensive, but they're no good for aviation use because they have only one or two channels, meaning they are relatively slow to pinpoint your position and cannot track satellites while moving at high speeds. Like sequential receivers, multiplex receivers switch back and forth between satellites being tracked. While they can follow more satellites than sequential units, they are still slower and less accurate than continuous receivers. As the name suggests, the latter can track several satellites at the same time on a continuous basis.
Continuous receivers require a minimum of four channels to read the data from three satellites.
Five channels allow the receiver to follow four satellites simultaneously and so on. Code correlation receivers determine position by processing information from the code that is transmitted by the satellites. These receivers, which are the most common and the most affordable, are accurate to within about five meters. Carrier phase receivers determine position by processing the satellite signals' carrier phase. Such receivers may be accurate to within a few centimeters, but they are very costly and impractical for most uses.