Article: 4189 of sci.geo.satellite-nav From: Carsten Kurz Newsgroups: sci.geo.satellite-nav Subject: Re: Consumer grade and pseudorange? Date: Fri, 24 Aug 2001 16:01:23 +0200 Organization: Audio Visual Systems Lines: 42 Message-ID: <3B865E33.513D724@t-online.de> References: <998658330.864972@asterix.tee.gr> Reply-To: audiovisual@t-online.de Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8bit X-Trace: news.t-online.com 998664657 03 16167 E7pKSn4bTBAFYc 010824 14:50:57 X-Complaints-To: abuse@t-online.com X-Sender: 02238967924-0001@t-dialin.net X-Mailer: Mozilla 4.73 [de]C-CCK-MCD DT (Win98; U) X-Accept-Language: de Path: news.meer.net!sea-read.news.verio.net!dfw-artgen.news.verio.net!iad-peer.news.verio.net!news.verio.net!fu-berlin.de!newsfeed01.sul.t-online.de!newsfeed00.sul.t-online.de!newsmm00.sul.t-online.com!t-online.de!news.t-online.com!not-for-mail Xref: archive.mv.meer.net sci.geo.satellite-nav:4189 > Is the above true in general? > What if we also take into account the time? > What if we also take into account the sat's used in each solution? Most GPS Receivers will not output the sat PRNs used in the solution. Remember that the satellites-in-view message doesn not contain information about the specific sats used in the solution and how they were weighted. Doing a simple koordinate based DGPS will only work decently for very short distances between the two receivers, and only if you can manage that both receivers see the same sats. This scheme could be used when SA was still on, but now I don't think that any positive results can be obtained. These severe constraints render any effort towards that idea useless to my opinion. Remember that conventional DGPS receivers cost not too much more than a second GPS receiver being needed for homebrew DGPS. WAAS even comes for free in the current range of receivers. Conventional realtime DGPS will only get you down to 1-3metres, not too far away from good DGPS less receivers, and about the same with WAAS DGPS. Anybody that needs or wants sub-meter accuracy simply needs to do post-processing on raw data. The 2-3m range seems to be the definite limit of the current GPS system using common realtime receiver techniques. Seems that postprocessing software is coming out of experimental state, there are quite a few cheaper commercial programs already, and there will be more and more in the future. USA has their CORSE stations, and as far as I can see, Europe already has a nice network of EUREF stations (some even provide hourly updates) so it seems that this will be the way to go sub-meter. -Carsten -- Audio Visual Systems fon: +49 (0)2238 967926 Carsten Kurz fax: +49 (0)2238 967925 Fasanenweg 38a email: audiovisual@t-online.de 50259 Pulheim / Germany WGS84:N50°58'44.7" E06°47'03.5"