WAAS- Wide Area Augmentation System
if you have a unit that is WAAS enabled and your in a WAAS supported area, like we are, the accuracy goes to 5m or less.
LAAS- Local Area Augmentation System
I was involved in maintaining and upgrading a LAAS station at EWR for an experimental GPS based landing system to replace the ILS currently being used. a Honeywell/Pelorus Navigation team effort. put a MD-80 on the ground at EWR within a 3ft target on the runway. the pilot refered to the landing as riding on a rail to the ground.
coming to a airport near you in about 7-10 years. our fleet has MMRs(mulitmode receivers) for multi landing systems just waiting for it to arrive.