STUDY ON POSITIONING ACCURACY OF PORTABLE GPS SURVEYING AFTER THE CESSATION OF GPS SELECTIVE AVAILABILITY (SA)

Portable GPS has never been used in practical surveying because of its poor accuracy, but it has great potential for practical use due to its low cost equipment. We proposed a method to improve positioning accuracy in portable GPS surveying by adopting differential GPS in which four active signals from four satellites are fixed during the period of measurement at the two end stations. On May 1, 2000, the intentional degradation of the GPS signals, known as Selective Availability (SA), was turned off. This study aims to compare the results of the positioning accuracy before and after the cessation of SA. The experimental results indicated that our proposal of positioning accuracy is still applicable even after the termination of SA.