Article: 10475 of sci.geo.satellite-nav From: Richard Kaszeta Newsgroups: sci.geo.satellite-nav Subject: Re: WAAS Capability Hand Helds Date: 23 May 2001 16:10:16 -0500 Organization: University of MN ME Dept Lines: 51 Sender: kaszeta@bofh.me.umn.edu Message-ID: References: <3B0B90A0.F8180BA1@pcug.org.au> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Trace: laurel.tc.umn.edu 990652217 27771 128.101.140.133 (23 May 2001 21:10:17 GMT) X-Complaints-To: usenet@laurel.tc.umn.edu User-Agent: Gnus/5.0803 (Gnus v5.8.3) Emacs/20.7 Path: news.meer.net!sea-read.news.verio.net!dfw-artgen.news.verio.net!dfw-peer.news.verio.net!news.verio.net!stl-feed.news.verio.net!news.cc.ukans.edu!logbridge.uoregon.edu!hardy.tc.umn.edu!laurel.tc.umn.edu!not-for-mail Xref: archive.mv.meer.net sci.geo.satellite-nav:10475 imallett writes: > Can anyone comment on the performance etc of the WAAS capable hand helds > that are now coming on the market - such as the Garmin 295? From my own experiments, I'd say that the answer is "Your Mileage May Vary." During my recent travels, I've used my eTrex Vista in the following areas: 1. Minnesota: It's virtually impossible to get any WAAS satellites here, although you can get them if you really work at it. Standing on the roof of my building at the University of Minnesota, with good clear skies and good sky view, leaving the receiver sitting perfectly still for ~30 minutes or so will get you a lock on a WAAS satellite, and you'll get correction data. With a lock on 9 satellites, all reporting WAAS corrected data, I got a reported error of 24 ft. Under near-identical circumstances with WAAS off and 9 satellites locked in, the reported error was 16ft. Moving the reciever *at all* resulted in loss of WAAS data. So here, WAAS isn't usable, and seems to increase error. 2. Cleveland, OH: Similar experience to Minnesota. At Lewis Field, with good sky view and clear weather, I got 8 satellites for a reported error of 32 ft, WAAS enabled, although it only took about 10 minutes to get a lock. With WAAS disabled and the same satellite geometry, the reported error was 26 ft. One improvement over Minnesota: if you kept a good skyview you could move around and not lose WAAS lock. 3. Hanover, NH: Here I had no trouble getting a WAAS lock, and as long I had decent sky view I wouldn't lose WAAS lock, and if I did, it would regain lock fairly easily. Parked in the downtown Hanover parking ramp, I got 9 satellites locked, all reporting WAAS corrections, with a reported error of 10 ft. Disabling WAAS, the error increased to 16 ft. Most anytime I was out in the open WAAS worked, while it virtually never worked when I was in forested areas with light-to-medium tree cover. So the answer is "It depends." If you're in an area with good sky view that's not in the middle of the US, I'd leave it enabled, otherwise, don't bother. Note that I was busy with my job, so I didn't have time to actually do any of this scientifically. -- Richard W Kaszeta Engineer rich@kaszeta.org University of MN, ME Dept http://www.kaszeta.org/rich