Wide Area Augmentation System (WAAS)
WAAS is an air navigation aid developed by the FAA that uses a combination of ground based reference stations to augment GPS satellite signals, with the original goal of enabling aircraft to rely on GPS for all phases of flight, including precision landing approaches at any airport within the coverage area.
In the process, they made all WAAS enabled GPS devices about five times more accurate than they were before WAAS. This is pretty good stuff and it's available, for free, to anyone with a WAAS enabled GPS device.
We made very good use of WAAS when placing mining claim monument stakes on claimsites recently. We used a hand-held DeLorme GPS unit that is WAAS enabled and found its accuracy level more than adequate for the job.
Usually it came within several feet of old government survey markers, where those existed.
Besides staking mining claims in the right spot, WAAS coordinates can be useful in getting back to a precise spot that you might really want to get back to someday.
Let's say an ore sample collected someplace out there turns out to assay with dynamite readings ... it would be more than nice to be able to go back to precisely that spot again.
WAAS enabled GPS - Don't leave home without it!