I having been digging in the FAA site concerning the new WAAS service, which is supposed to provide additional accuracy. The extra data information is broadcast by a Geosynchonise satellite. In other words, one of the satellites not part of the GPS constellation, but parked in fixed orbit over the equator, like AOR-W. The FAA bulletin advertises 7 meter (22 feet of precision), vertically and horizontaly. MY Garmin 48, generally shows about 20 feet of estimated precision error(EPE). I take that to mean they are about equal, although my machine does not decode the WAAS signals. A good comparison of WAAS versus a non WAAS equipped machine does not seem to be avialable. I would hazard a guess that the newer 12 channel garmins without WAAS are near as accurate as the newest with WAAS. The FAA site implies that the WAAS provides better vertical precision, which may not be of much interest to us boaters and some addtional reliability messages which MAY be of some value to us. I have a friend with a Garmin 76 that has the WAAS and he was getting EPE's of about 15 feet, with WAAS turned on and about 25 feet with it turned off. Capt. Mike Maurice Near Portland Oregon.

At 10:21 AM 08/19/2001 -0400, Michael Maurice wrote: >A good comparison of WAAS versus a non WAAS equipped machine does not seem >to be avialable. I would hazard a guess that the newer 12 channel garmins >without WAAS are near as accurate as the newest with WAAS. <<< snip>>> > I have a friend with a Garmin 76 that has the WAAS and he was getting >EPE's of about 15 feet, with WAAS turned on and about 25 feet with it >turned off. REPLY Mike isa correct. My survey partner had the opprotunity to compare the gArmin 12 channel receiver with DGPS and a 12 channel WAAS receiver side by side. Positioning differences amounted to less than 10 feet. Sine he and I both have DGPS and confine our survey work to areas covered by differential beacons, we don't see a need to upgrade at this time. However, for those who did not have Differential beacon receivers the new WAAS is definitely more accurate. Mind you; unless you actually measure the EXACT location of the antenna on your hull in relation to the hull perimeter and the props and other vulnerable hull parts the degree of accuracy is a moot point. And of course, this will not do anything about correcting for chart datum errors or lack of a known datum. Oh yes, some charts are still presented despite the fract these areas are not portyrayed with a KNOWN datum. But that is another whole chapter. . . - later! Cheers Arild