On Fri, Feb 6, 2009 at 2:09 PM, Tom Lancaster <tom at grubbyconsulting.com> wrote: > On Fri, Feb 6, 2009 at 1:31 PM, Jean Christophe Andr? > <jean-christophe.andre at auf.org> wrote: >> Tom Lancaster a ?crit : >>> On Fri, Feb 6, 2009 at 10:25 AM, Nguyen Vu Hung <vuhung16plus at gmail.com> >>> wrote: >>> >>>> I will do it when I return to Vietnam. However, I heard that GPS receivers >>>> in Vietnam may get 9m of error in minimum. Is that right? >>>> >>> Why would VN be any different than another point on the globe? >> May be because there is less GPS service satellites covering our area? > > FWIW I routinely pick up 10 satellites here, often more (up to 18, I > think). Accuracy only drops in built-up areas with poor sight lines.
Here's an interesting site that gives information on stuff in the sky. According to this page there are 14 US GPS satellites in view right now. http://www.calsky.com/?GPS= Tom > >> >>> For non-military use the US GPS system only has 10m accuracy. In practice >>> (in my experience) the accuracy appears to be somewhat better than that. >>> >> Yes and it's easy to explain: we would only get the precision they allow >> us to get if we used GPS in the conventional way. But in fact you can >> triangulate your coordinates with more than 4 satellites (3 for >> trilateration, 1 for time correction) and finally get a far better >> precision (with up to 12 or even 20 satellites with modern receivers). >> And that's exactly what do most modern GPS receivers, should I say "of >> course" ?! ;-) >> >> As usual, more detailed informations are available here: >> http://en.wikipedia.org/wiki/GPS >> And this time also in Vietnamese: :-) >> http://vi.wikipedia.org/wiki/H?_th?ng_??nh_v?_to?n_c?u >> >> -- >> Jean Christophe "????" ANDR? ? ? ? Responsable technique r?gional >> Bureau Asie-Pacifique (BAP) ? ? ? http://www.asie-pacifique.auf.org/ >> Agence universitaire de la Francophonie (AuF) ? ? ? http://www.auf.org/ >> Adresse postale : AUF, 21 L? Th?nh T?ng, T.T. Ho?n Ki?m, H? N?i, Vi?t Nam >> T?l. : +84 4 9331108 ? Fax : +84 4 8247383 ? Cellul. : +84 91 3248747 >> ? Note personnelle: merci d'?viter de m'envoyer des fichiers PowerPoint ? >> ? ou Word, cf http://www.gnu.org/philosophy/no-word-attachments.fr.html ? >> >> >> >> _______________________________________________ >> POST RULES : http://wiki.hanoilug.org/hanoilug:mailing_list_guidelines >> _______________________________________________ >> HanoiLUG mailing lists: http://lists.hanoilug.org/ >> HanoiLUG wiki: http://wiki.hanoilug.org/ >> HanoiLUG blog: http://blog.hanoilug.org/ >> >
