Simplify the following text for a Grade 8 native English-speaking person.
Original: One of the most significant error sources is the GPS receiver 's clock . Because of the very large value of the speed of light , c , the estimated distances from the GPS receiver to the satellites , the pseudoranges , are very sensitive to errors in the GPS receiver clock ; for example an error of one microsecond ( 0.000 001 second ) corresponds to an error of 300 m. This suggests that an extremely accurate and expensive clock is required for the GPS receiver to work .
Simplified: A GPS receiver can calculate its position many times in one second .