Xref: utzoo rec.boats:1039 sci.space.shuttle:1795 rec.aviation:10365 Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!mailrus!cornell!uw-beaver!tektronix!pogo!rgrove From: rgrove@pogo.GPID.TEK.COM (Robert Grove) Newsgroups: rec.boats,sci.space.shuttle,rec.aviation Subject: Re: NAVSTAR Message-ID: <6194@pogo.GPID.TEK.COM> Date: 28 Oct 88 17:41:35 GMT References: <1736@nunki.usc.edu> <172@axecore.UUCP> Reply-To: rgrove@pogo.GPID.TEK.COM (Robert Grove) Organization: Tektronix Inc., Wilsonville, Oregon Lines: 31 In article <172@axecore.UUCP> lloyd@axecore.UUCP (Lloyd Buchanan) writes: > >I presume NAVSTAR works as a variant of the same hyperbolic radionavigation >as LORAN. This means that a receiver can only determine its position in >relation to the transmitters. LORAN is no problem as the transmitters >are in fixed, known positions. LORAN, which does calculate a distance difference from 2 stations to place you on a hyperbolic line, then does the same thing with two other stations and which determines your position by where the hyperbolic lines cross, requires a minimum of three transmitters to determine your position. NAVSTAR may not be the same as the older NAVSAT but, it probably works in the same way; if so, only one NAVSAT is required to get a position but, you need to already know, within a degree or so, where you are. My guess would be that the NAVSTAR station transmits its orbital information on a couple of different frequecies. This is done to resolve refraction error. By measuring the doppler of the transmission and, by knowing the orbital information of satellite and, roughly where you are, you can tell exactly where you are. Note that satellite passes that are closer to directly overhead are the least useful as there is no way to resolve which side the pass was on from the transmitted information. You need to already know that. I assume that the NAVSTARS will be in polar orbit as were the NAVSATs. -- Robert Grove rgrove@pogo.gpid.tek.com.uucp | {anybackbone != ihnp4}!tektronix!pogo!rgrove