No, under 5m is the basic accuracy you get from an unassisted dual-band WAAS GPS on the ground, like in a standalone navigation device. You have to remember th

No, under 5m is the basic accuracy you get from an unassisted dual-band WAAS GPS on the ground, like in a standalone navigation device. You have to remember that many of the error sources have been improved at the system level since GPS first launched: 1. WAAS and dual-frequency receivers correct the largest source of error, which is varying signal delay through the ionosphere. WAAS is broadcast on the same frequency as regular L1 signals, so receiving it and applying the corrections requires no hardware changes. 2. Satellite ephemeris and clock errors: New satellites have laser retro-reflectors so the control segment can measure their position more accurately. The control segment also uploads ephemerides more frequently, so they are fresher. Satellite clocks have been improved. Once you correct for those, the main limitation is resolution in measuring time of arrival, which is where the high chip-rate military code helps. But carrier phase tracking can help here. I don't know why commenters in this thread are quoting "30 meters". Maybe they got confused with the 3-sigma confidence in feet and then assumed meters as the units? You really have to be in an environment with serious multi path interference or GPS jammers or an extremely naive receiver implementation to get accuracy that bad.