Article: 18727 of sci.geo.satellite-nav From: Stichting ST Newsgroups: sci.geo.satellite-nav Subject: Re: Using Garmin consumer GPS to produce DGPS data. Date: Tue, 12 Mar 2002 19:34:49 +0100 Message-ID: References: <3C8CD50B.3030504@madeupdomain.com> X-Newsreader: Forte Agent 1.9/32.560 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Lines: 36 NNTP-Posting-Host: 194.109.247.185 X-Trace: 1015957649 dreader3.news.xs4all.nl 24808 194.109.247.185 Path: news.meer.net!ord-read.news.verio.net!dfw-artgen!iad-peer.news.verio.net!news.verio.net!news.maxwell.syr.edu!transit.news.xs4all.nl!rhinewceros.xs4all.nl!not-for-mail Xref: archive.mv.meer.net sci.geo.satellite-nav:18727 On Tue, 12 Mar 2002 17:20:55 GMT, Wolfgang Rupprecht wrote: > >simon writes: >> It appears true that you can use Garmin consumer grade GPS's in an >> unsupported mode to output the phase/timing information of the raw >> satelite signals. I did this last weekend with async!! >> http://artico.lma.fi.upm.es/numerico/miembros/antonio/async/ > >Neat! What model/firmware_version did you try it with? > >Could you find some postprocessing code to try it with? Did it make a >big difference? > I am not Simon but I tried it out last weeks with my GPS12. Took measures from my rooftop for 1 hour on two different occasions, days between. The first one (without Doppler ) and good DOP (mostly 2 short time 13) gave me N 52 9 17.68234 E 4 29 13.29355 53.0637 for double diff float solution with sigma's [mm] of 2.8 6.2 3.0 the second one with doppler (and also phase and pseudo of course) gave N 52 9 17.69007 E 4 29 13.29382 53.5705 For postprocessing data I used the ref station DELFT University (netherlands) about 20 km away. You see: you need a lot of registering time to get an accuracy beneath 1 meter!!!! The most pronounced is the effect in altitude; very much better than expected. Piet Vogelaar PS one of these days I will take measures of a know (within 1 cm) point and see what that boils down to.