Folks, I'm in the process of preparing material for a presentation/class on GPS. I'm a bit intrigued by the two different approaches to improving the accuracy of GPS, namely DGPS (the Coast Guard's solution), and WAAS (the FAA's alternative). I understand the difference between the two approaches but question the need for two different solutions to the same problem. The best response to that issue that I've been able to locate on the web is by the Coast Guard at www.navcen.uscg.gov/gps/WAAS-DGPS.htm. As I read between the lines in that text, and other references, I get the distinct impression that we have two government agencies competing with each other. Can any of the list members provide me with any history or insight (i.e. gossip, rumor, innuendo, dirt, etc.) on this issue? Thanks. Mac

You basically have it correct. There is a little more to it though. First WAAS is not universal. You have to have the ground station infrastructure and satellite view. Thus WAAS data in the far north and rare places is lacking. (One could argue this is not very important as such places also have lousy charts so the increased accuracy is of little use) DGPS can be set up anywhere and requires little infrastructure. DGPS was also here first and was widely available in at least larger population centers. The other side of the coin is that WAAS is a capablity integrated into the system and integral to the receivers. DGPS is a bolt on with significant costs. Note that there are international maritime agreements that institutionalize DGPS. Another interesting thing is that the pseudosatellites included in the full aeronautical proposition could serve the role of DGPS. In recreational boating I can't believe the outcome is in doubt. WAAS will be universal and DGPS almost never seen. The commercial industry will likely utilize DGPS though WAAS will probably infiltrate by being included in the base equipment. None of this of course is final. As the european system comes on line and advanced capabilities are added to GPS we will get a whole new set of capabilities. I would not be surprised to see WAAS and DGPS obsoleted by these new capabilities. When the base system gets to a meter or so why any augmentation for nautical purposes? There is a lot of historical discussion on this on some of the internet lists. I would think their may be some on TWL. Also a lot on rec.boats.cruising. You might want to check that archive. Perhaps on the old Compuserve Sailing list as well though I do not know if that is archived. If I remember at the time the CG ducked the issue simply stating that WAAS was an aeronautical system and DGPS a nautical one. There are a very nice set of articles at Stanford - http://waas.stanford.edu/pubs/index.htm Don't know of a direct comparison but it might be buried there. It was a wonderful opportunity for an integrated standard...but no cigar. Jim Donohue > -----Original Message----- > From: trawler-world-list-bounces@lists.samurai.com > [mailto:trawler-world-list-bounces@lists.samurai.com] On > Behalf Of N.R. McBurney II > Sent: Wednesday, April 14, 2004 8:54 AM > To: trawler-world-list@lists.samurai.com; mainship@yahoogroups.com > Subject: TWL: DGPS vs. WASS > > > Folks, > > > I get the distinct impression that we have > two government agencies competing with each other. > > > > Can any of the list members provide me with any history or > insight (i.e. gossip, rumor, innuendo, dirt, etc.) on this issue? > > > > Thanks. > > > > Mac > _______________________________________________ > http://lists.samurai.com/mailman/listinfo/trawler-world-list > > To Unsubscribe send email to > trawler-world-list-request@lists.samurai.com > Include the word "Unsubscribe" (and nothing else) in the > subject or body of the message. > >

DGPS need not be expensive. Checkout the Furuno GPS37 which incorporates all three civilian mode. Just a happy owner. Ron Rogers

I would guess that one is getting obsolete. It dates back a ways. Note the literature on the Furuno site states that the DGPS mode is better than the WAAS mode because the WAAS mode is still experimental and it may not always be available. That of course went away last summer. It also appears to have the accuracy wrong. Anybody know of any other compound units? Jim > > Behalf Of Ron Rogers > Sent: Saturday, April 17, 2004 12:37 PM > To: Jim Donohue; 'N.R. McBurney II'; > > > > DGPS need not be expensive. Checkout the Furuno GPS37 which > incorporates all three civilian mode. Just a happy owner. Ron > Rogers _______________________________________________ > http://lists.samurai.com/mailman/listinfo/trawler-world-list > >

Except for a commercial model most sites don't list, the GPS37 is Furuno's latest. Remembering an email from Arild, it will be a few years before models come out which will be able to receive the signals of newer satellites. Some European models can pick up Russian GLOSNAS signals which used to have a "sweet spot" over the US East Coast, but it's hard to imagine a requirement for greater accuracy for pleasure navigation. Ron Rogers ----- Original Message ----- From: "Jim Donohue" <jim_donohue@computer.org> | I would guess that one is getting obsolete. It dates back a ways. Note | the literature on the Furuno site states that the DGPS mode is better | than the WAAS mode because the WAAS mode is still experimental and it | may not always be available. That of course went away last summer. It | also appears to have the accuracy wrong. Anybody know of any other | compound units? | | > Behalf Of Ron Rogers | > | > DGPS need not be expensive. Checkout the Furuno GPS37 which | > incorporates all three civilian mode. Just a happy owner.