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Photographing satellites against background stars was developed as a geodetic
positioning technique in the 1960s. See
, an excerpt from the venerable
Guide to GPS Positioning  (Warning: 106 MB)
for a brief overview of this early satellite positioning technique.
-- Richard Langley
   Professor of Geodesy and Precision Navigation

On Thu, 6 Dec 2007 frankreed@historicalatlas.net wrote:

>
>Apologies for drifting off-topic here...
>
>There's another way to do automatic navigation: you let the satellite find
>YOU. Ships at sea are easy to detect. A handful of satellites can track
>every vessel on the face of the Earth assuming they're emitting some radio
>noise (the electrical systems of any modern ship's engine produce enough
>radio noise). Then when you need your position, you call up the satellite
>and ask. And needless to say, you can ask it to tell you where your
>"friends" are, too. There have been reports of such systems in actual use
>for years. There are sets of satellites, supposedly operated by the US NRO,
>that travel together in small groups. It's a bit eery: you can see three
>little "stars" gliding across the sky together in a triangle a few degrees
>across if you know where and when to look (google "NOSS trios").
>
>Speaking of satellites, how about using them for small-craft navigation?
>And, no, not GPS satellites. I'm talking about visual observations of low
>orbit satellites. Satellite positions are as predictable as the Moon's, as
>long as you avoid objects which maneuver frequently, like the International
>Space Station. And if using a computer isn't cheating, then you can get a
>line of position by observing a satellite's position in the sky (I'm
>picturing tracking it with binoculars and looking for close approaches to
>moderately bright stars). If I observe a satellite that's 500 nautical miles
>above me, and if I can get its position relative to some star accurate to a
>tenth of a degree, which should be possible, then I can get a line of
>position accurate to about 1 nautical mile. If I have a rough DR position to
>start with, there shouldn't be any problem with mistaken satellite
>identities.
>
> -FER
>
>>
>


===============================================================================
 Richard B. Langley                            E-mail: lang@unb.ca
 Geodetic Research Laboratory                  Web: http://www.unb.ca/GGE/
 Dept. of Geodesy and Geomatics Engineering    Phone:    +1 506 453-5142
 University of New Brunswick                   Fax:      +1 506 453-4943
 Fredericton, N.B., Canada  E3B 5A3
     Fredericton?  Where's that?  See: http://www.city.fredericton.nb.ca/
===============================================================================

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