The accuracy of the GPS signal in space is actually the same for both the civilian GPS service (SPS) and the military GPS service (PPS). However, SPS broadcasts on one frequency, while PPS uses two. This means military users can perform ionospheric correction, a technique that reduces radio degradation caused by the Earth’s atmosphere. With less degradation, PPS provides better accuracy than the basic SPS.
Many users enhance the basic SPS with local or regional augmentations. Such systems boost civilian GPS accuracy beyond that of PPS.
The ongoing GPS modernization program is adding new civilian signals and frequencies to the GPS satellites, enabling ionospheric correction for all users. Eventually, the accuracy difference between military and civilian GPS will disappear. But military GPS will continue to provide important advantages in terms of enhanced security and jam resistance.