What is the role of pseudoranges in GPS positioning?

Pseudoranges are estimates of the distance between a GPS receiver and a GPS satellite. They are a key component in determining the receiver's position. A GPS receiver calculates its position by measuring the time it takes for signals to travel from multiple GPS satellites to the receiver. The distance to each satellite is then calculated by multiplying the signal travel time by the speed of light. However, these distances are called "pseudoranges" rather than true ranges because the receiver's clock is not perfectly synchronized with the satellite's clock. This time difference introduces an error in the distance calculation. The receiver uses signals from at least four satellites to solve for its three-dimensional position (latitude, longitude, altitude) and the receiver clock offset. By solving for the clock offset, the pseudoranges are effectively corrected to provide a more accurate position. The more satellites a receiver can track, the more accurate the position fix will be. The term "pseudo" refers to the fact that these ranges are not perfectly accurate due to the clock error, but they are still essential for calculating the receiver's position. For example, if a GPS receiver measures a pseudorange of 20,000 kilometers to one satellite, and 21,000 kilometers to another, this information, along with pseudoranges to at least two more satellites, is used to calculate the receiver's location on Earth.