Article: 147497 of sci.geo.satellite-nav From: Antonio Tabernero Galan Newsgroups: sci.geo.satellite-nav Subject: Re: Garmin 12XL and raw data Date: Tue, 23 May 2000 11:52:21 +0200 Organization: Universidad Politecnica Madrid Lines: 56 Message-ID: <392A54D5.E531577E@fi.upm.es> References: <3920F24A.8FE410B2@nlr.nl> <3921e342_2@news1.prserv.net> <8gcd7j$b38$1@panix5.panix.com> NNTP-Posting-Host: hyundai.ls.fi.upm.es Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Trace: panoramix.fi.upm.es 959075614 15693 138.100.10.50 (23 May 2000 09:53:34 GMT) X-Complaints-To: news@panoramix.fi.upm.es NNTP-Posting-Date: 23 May 2000 09:53:34 GMT X-Mailer: Mozilla 4.61 [en] (X11; I; Linux 2.2.10 i686) X-Accept-Language: en Path: news1.meer.net!news3.best.com!news2.best.com!feed1.news.rcn.net!rcn!newsfeed.cwix.com!newsfeed.mathworks.com!news-ge.switch.ch!news.rediris.es!news-2.rediris.es!138.100.251.9.MISMATCH!news.upm.es!panoramix.fi.upm.es!not-for-mail Xref: news1.meer.net sci.geo.satellite-nav:147497 Kenneth Crudup wrote: > Does anyone know if the basic GPS 12 has this mode, too? > > -Kenny Yes. I have been playing with it a while and I can send /post to you more detailed information if you're interested. I was thrilled at the beginning considering the possibility of post processing data. However, I was quite disappointed when I examined more carefully the 0x38 records. While bits 14-21 (starting from 0) do correspond to a double with a good-looking value of about 20,000,000 (Pseudorange in meters), I found that at least in my Garmin12 (ver 4.00) those numbers were always increasing by about 6000 every second , as if all the sats and I were in an expansive universe. Consequently, after a 20 minute observation, the pseudoranges (by now pseudo-pseudoranges) had values around 35,000,000 (all of them), which didn't make much sense to me. I decided that a further coding of the data existed and reluctantly dropped the subject. That's why I have been nicely surprised with the last post from Sam Storm van Leeuwen reporting successful postprocessing of that data, and that's why I would appreciate his further commenting on those results: * Is there any additional corrections needed to get pseudoranges from record 0x38? * Could it be a version/unit-dependent problem? Has anyone gotten meaningful pseudoranges (without the ever-increasing trend) with a Garmin12 (version ?). I'd be glad to put together a report of what it is known about async messages in Garmin units containing raw data. Antonio PS: by the way, the increment in psedoranges (bits 14-21 of record 0x38) is similar -but not equal- to a float that appears in bits 0-3 in record 0x16. Could it be two different measures of the same quantity, let's say integrated Doppler vs. difference of pseudoranges?. This two numbers are also related to a counter placed in an unsigned long in bits 0-3 of record 0x38. This counter gets incremented by about 60-70,000,000 every second., and its increment is closely related (except for a factor) to the float in bits 0-3 of record 0x16. -- Antonio Tabernero Galan E-mail: ant@fi.upm.es Facultad de Informatica (UPM). 28660 Boadilla del Monte, Madrid, Spain. Article: 147497 of sci.geo.satellite-nav From: Antonio Tabernero Galan Newsgroups: sci.geo.satellite-nav Subject: Re: Garmin 12XL and raw data Date: Tue, 23 May 2000 11:52:21 +0200 Organization: Universidad Politecnica Madrid Lines: 56 Message-ID: <392A54D5.E531577E@fi.upm.es> References: <3920F24A.8FE410B2@nlr.nl> <3921e342_2@news1.prserv.net> <8gcd7j$b38$1@panix5.panix.com> NNTP-Posting-Host: hyundai.ls.fi.upm.es Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Trace: panoramix.fi.upm.es 959075614 15693 138.100.10.50 (23 May 2000 09:53:34 GMT) X-Complaints-To: news@panoramix.fi.upm.es NNTP-Posting-Date: 23 May 2000 09:53:34 GMT X-Mailer: Mozilla 4.61 [en] (X11; I; Linux 2.2.10 i686) X-Accept-Language: en Path: news1.meer.net!news3.best.com!news2.best.com!feed1.news.rcn.net!rcn!newsfeed.cwix.com!newsfeed.mathworks.com!news-ge.switch.ch!news.rediris.es!news-2.rediris.es!138.100.251.9.MISMATCH!news.upm.es!panoramix.fi.upm.es!not-for-mail Xref: news1.meer.net sci.geo.satellite-nav:147497 Kenneth Crudup wrote: > Does anyone know if the basic GPS 12 has this mode, too? > > -Kenny Yes. I have been playing with it a while and I can send /post to you more detailed information if you're interested. I was thrilled at the beginning considering the possibility of post processing data. However, I was quite disappointed when I examined more carefully the 0x38 records. While bits 14-21 (starting from 0) do correspond to a double with a good-looking value of about 20,000,000 (Pseudorange in meters), I found that at least in my Garmin12 (ver 4.00) those numbers were always increasing by about 6000 every second , as if all the sats and I were in an expansive universe. Consequently, after a 20 minute observation, the pseudoranges (by now pseudo-pseudoranges) had values around 35,000,000 (all of them), which didn't make much sense to me. I decided that a further coding of the data existed and reluctantly dropped the subject. That's why I have been nicely surprised with the last post from Sam Storm van Leeuwen reporting successful postprocessing of that data, and that's why I would appreciate his further commenting on those results: * Is there any additional corrections needed to get pseudoranges from record 0x38? * Could it be a version/unit-dependent problem? Has anyone gotten meaningful pseudoranges (without the ever-increasing trend) with a Garmin12 (version ?). I'd be glad to put together a report of what it is known about async messages in Garmin units containing raw data. Antonio PS: by the way, the increment in psedoranges (bits 14-21 of record 0x38) is similar -but not equal- to a float that appears in bits 0-3 in record 0x16. Could it be two different measures of the same quantity, let's say integrated Doppler vs. difference of pseudoranges?. This two numbers are also related to a counter placed in an unsigned long in bits 0-3 of record 0x38. This counter gets incremented by about 60-70,000,000 every second., and its increment is closely related (except for a factor) to the float in bits 0-3 of record 0x16. -- Antonio Tabernero Galan E-mail: ant@fi.upm.es Facultad de Informatica (UPM). 28660 Boadilla del Monte, Madrid, Spain.