Path: news.ccsf.jp!tomockey.ddo.jp!border1.nntp.dca.giganews.com!nntp.giganews.com!postnews.google.com!m42g2000yqb.googlegroups.com!not-for-mail From: RustyJames Newsgroups: alt.math,japan.sci.math,sci.math,sci.physics,sci.physics.relativity Subject: Re: GPS question Date: Tue, 24 Feb 2009 11:40:51 -0800 (PST) Organization: http://groups.google.com Lines: 101 Message-ID: References: <1faf92f1-847e-41c9-b6eb-09556cdeb0bc@t3g2000yqa.googlegroups.com> <9f09958d-1b9d-4951-8623-d76c3eb4e8de@w34g2000yqm.googlegroups.com> NNTP-Posting-Host: 168.174.253.221 Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: quoted-printable X-Trace: posting.google.com 1235504451 25388 127.0.0.1 (24 Feb 2009 19:40:51 GMT) X-Complaints-To: groups-abuse@google.com NNTP-Posting-Date: Tue, 24 Feb 2009 19:40:51 +0000 (UTC) Complaints-To: groups-abuse@google.com Injection-Info: m42g2000yqb.googlegroups.com; posting-host=168.174.253.221; posting-account=UmSM6QoAAAAHQsbQSpqx55ht5J9R5UV_ User-Agent: G2/1.0 X-HTTP-UserAgent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; .NET CLR 1.1.4322; InfoPath.1),gzip(gfe),gzip(gfe) Xref: news.ccsf.jp japan.sci.math:216 On Feb 23, 3:40=A0pm, Dono wrote: > On Feb 23, 12:33=A0pm, Cephalobus_alie...@comcast.net wrote: > > > > > > > On Feb 23, 12:49=A0pm, koobee.wub...@gmail.com wrote: > > > > On Feb 20, 4:33 am, "Jon" wrote: > > > > > Supposing three satellites transmit signals with time stamps that a= re picked > > > > up by a receiver. =A0If the clocks on the satellites are closely sy= nchronized, > > > > then > > > > > |AD|=3D|AB|+t_AB > > > > |BD|=3D|BC|+t_BC > > > > |CD|=3D|CA|+t_CA > > > > > Where > > > > A,B,C=3Dposition vectors of three satellites > > > > AB,BC,CA=3Ddistances between satellites > > > > t_AB,t_BC,t_CA=3Dtime differences between signals at D. > > > > D=3Dposition vector of receiver. > > > > > Once |AD|,|BD|,|CD| are found, the coordinates of D can be derived. > > > > > Is this how it is done? > > > > > summarized at > > > > >http://mypeoplepc.com/members/jon8338/math/id8.html > > > > You need four satellites where each satellite should know its time an= d > > > position. =A0Time can just be a counter with all the satellites > > > synchronized to within a count of each other. =A0Each satellite then > > > just broadcast its time and position information as almanac signal to > > > whoever wants to receive it. > > > > Since the distance is traveled by light with a known speed, you can > > > then easily form a set of four equations with four unknowns. =A0The f= our > > > unknowns are your time (relative to the counter in each satellite) an= d > > > position. > > > > ** =A0c^2 (t1 =96 t)^2 =3D (x1 =96 x)^2 + (y1 =96 y)^2 + (z1 =96 z)^2 > > > ** =A0c^2 (t2 =96 t)^2 =3D (x2 =96 x)^2 + (y2 =96 y)^2 + (z2 =96 z)^2 > > > ** =A0c^2 (t3 =96 t)^2 =3D (x3 =96 x)^2 + (y3 =96 y)^2 + (z3 =96 z)^2 > > > ** =A0c^2 (t4 =96 t)^2 =3D (x4 =96 x)^2 + (y4 =96 y)^2 + (z4 =96 z)^2 > > > > Where > > > > ** =A0(t1, x1, y1, z1) =3D Time and position of satellite 1 > > > ** =A0(t2, x2, y2, z2) =3D Time and position of satellite 2 > > > ** =A0(t3, x3, y3, z3) =3D Time and position of satellite 3 > > > ** =A0(t4, x4, y4, z4) =3D Time and position of satellite 4 > > > ** =A0(t, x, y, z) =3D Time and position of the receiver > > > > Notice that relativistic effect is never needed. > > > Currently, only Block IIR satellites are capable of autonomous > > position monitoring and synchronization independent of the ground > > control segment. This capability allows Block IIR satellites to > > mutually correct their clocks and ephemerides information for a > > period of up to several months should the ground segment be > > knocked out by, say, nuclear war. For optimum performance under > > non-wartime conditions, "ground truth" comparisons are still > > performed on a daily basis to correct the satellites for drift. > > > GPS satellites before the Block IIR series are incapable of such > > mutual correction, and require monitoring and daily corrections > > by the Ground Segment. > > > Satellite control requires that the Space Segment and Ground > > Segment clocks be synchronized. The only practical way of > > synchronizing the world-wide network of ground stations is to > > use the network of GPS satellites to disseminate time. The only > > way to use the networks of GPS satellites to disseminate time is > > if the satellite clocks are adjusted via the GR correction so > > that they beat in time with Earth clocks. > > > Jerry- Hide quoted text - > > > - Show quoted text - > > Jerry > > According to Dave's post (see above), the satellites in relative > motion (at about 6.7km/s) so the Kobee-Wublee idiot needs to > understand that, even with Block IIR, the relativistic corrections are > still needed.- Hide quoted text - > > - Show quoted text - I thought they were geostationary I believe their geosynchronous to the earths rotation