PRN133 ranging now useable for SoL, at non precision approach level

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.

For randomly generated 1023-bit codes we should expect collisions around
32 (sqrt(1024)), but since the codes can be selected by hand, they can
get away with approximately twice as many without having problems with
cross-correlation, with or without doppler corrections.

Several people have noted that you could theoretically get twice as many
sats if you set them up in pairs on opposite side of the globe, but
since there's no explicit sat nr in the transmitted msg, this won't work
with any currently deployed gps receivers.

(In theory, as long as the pairs were not exactly opposite, you should
be able to determine which hemisphere was the correct one by looking at
the residual errors for each of them?)

Terje
--
- Terje.Mathisen at tmsw.no
"almost all programming can be viewed as an exercise in caching"