On 2011-11-02 09:43 , Terje Mathisen wrote:
Alan Browne wrote:
On 2011-11-01 19:54 , Ed M. wrote:
On Nov 1, 3:21 pm, Alan
wrote:

That wouldn't fly far - there are only so many viable gold codes -
though possibly many more on L5 with its longer code length.


There are actually around 500 balanced (roughly equal number of 0s and

To avoid x-correlation there are only 35 or so. Don't recall the correct
number.

I have read a white paper which stated that the number of available Gold
codes was (afair) in the 60-70 range.

The number of "suitable codes" is 37. Again, x-correlation is the issue.

http://www.kowoma.de/en/gps/signals.htm as we discussed here some months
ago.

As I've stated in the past (and HIPAR states in this thread) one could
put satellites in opposition in the same plane and use the codes twice.

A quick scan (meaning I might have read it wrong) of ICD-200 data frames
doesn't appear to name the transmitting SV. - which would help
"unconfuse" the receiver (would need two almanacs per PRN). Acquisition
of PRN, eg: 23, would require knowledge of both almanacs and careful
attention to the ephemeris used if there is no other means of
identifying which is which. (Of course with reliable init position and
time, this would be unambiguous. For a cold start it wouldn't matter:
search a PRN and if it comes up it's one of the two). Problem is how to
store two almanacs per PRN, acquire and track without screwing up.
Could require an analysis of several satellite positions to
unambiguously select.

In brief, the PRN is the identifier for the satellite. (Almanac data
identifies the satellite for the data set (In the convoluted definition
of subframes 4 and 5 which carry a lot of almanac and other data ...
over a 12.5 minute cycle)).

http://www.navcen.uscg.gov/pubs/gps/...D200Cw1234.pdf

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