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?
> 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 ? -------------- section suivante -------------- Une pi?ce jointe non texte a ?t? nettoy?e... Nom: signature.asc Type: application/pgp-signature Taille: 260 octets Desc: OpenPGP digital signature Url: http://lists.hanoilug.org/pipermail/hanoilug/attachments/20090206/59498701/attachment.pgp
