... written for Panbo by Ben Ellison and posted on Aug 2, 2007
I just learned that on July 31 (or July 16, according to this Trimble PDF), the FAA decommissioned WAAS satellites 122 (#35) and 134 (#47), and that at least some marine GPS receivers are not able to recognize the remaining two correction-sending birds, 135 (#45 48) and the new 138 (#51). In other words, your plotter may not be showing your position quite as accurately as you’re used to. Take care, and please report in about your WAAS status. There’s a bit of info about this here, and a good explanation of WAAS here. And maybe you can figure out what the FAA is up to here.
PS 8/4: I’ve added the WAAS satellite service numbers—the # you should see on your GPS’s status screen—to the “PRN” numbers cited above and in the technical notices. Learning those numbers (thanks to Wikipedia) means that the Garmin GPS17 I tested yesterdaywas seeing the latest #51 satellite, which is the Telesat in geosynchronous orbit at 107W, and may be the only bird visible way up here in the Northeast. #48 is the PanAmSat at 133W and together they are supposed to give most of the U.S. redundant coverage. I still don’t know if the Garmin was actually receiving WAAS corrections. Nor am I convinced that a possible lack of WAAS makes much difference to marine navigation, given how good the uncorrected signals are.