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"

On Nov 1, 2:47*pm, HIPAR wrote:

Regarding *WDGPS, *I really don't understand who actually controls
access to the system. *If NASA operates the core system, what kind of
agreement does the US government have with Deere allowing them
exclusive commercial marketing rights under the Starfire trademark?
NASA/JPL doesn't say much about that.

--- *CHAS

JPL alludes to commercial opportunities on their site, but don't give
specifics of licensing, fees, etc. Clicking on the "Customer Portal"
tab yields a certificate error message.

http://www.gdgps.net/system-desc/network.html

"The core of the GDGPS network is the NASA Global GPS Network (GGN), a
JPL-owned and operated network of roughly 70 geodetic-quality, dual
frequency receivers, distributed globally. Additional real-time sites
are contributed by a variety of U.S. and international partner
organizations. The result is the world's largest real-time GPS
tracking network, with more than 100 global sites (as of October
2006). All these sites stream their GPS measurements at 1 Hz to the
GDGPS Operation Centers (GOCs), where it is processed and analyzed in
real-time.

.. . . The GDGPS system is proud to count 4 national timing
laboratories among it contributing network partners. In particular,
the United States Naval Observatory (USNO) contributes two monitoring
sites driven by its Master Clock, allowing the GDGPS System to provide
its global users the most accurate real-time realization of USNO UTC.

.. . . We continue to expand our network, and welcome contributions
from interested organizations. We offer our network partners a variety
of benefits, including real-time positioning, timing, and
environmental monitoring, as well as data archiving and data
distribution through the NASA CDDIS facility."

http://www.gdgps.net/applications/index.html

"The GDGPS System produces differential corrections to the GPS
broadcast ephemeris with unparelleled accuracy and seamless global
validity. Various GDGPS technology components and data products are
being used by nearly all of the providers of premium global
differential corrections. The underlying software and algorithms are
being used by the FAA's Wide Area Augmentation System (WAAS), and its
Japanese counterpart, MSAS. "

http://www.gdgps.net/system-desc/references.html

Kevin Dixon, "StarFi A Global SBAS for Sub-Decimeter Precise Point
Positioning," ION GNSS 2006, Fort Worth, TX, September 2006,
http://www.gdgps.net/system-desc/papers/starfire.pdf

"The central processing hubs are based upon a version of the Real Time
GIPSY (RTG) suite, originally developed by the Jet Propulsion
Laboratory for precise real time orbit and clock determination of
GNSS. This has been refined to optimize positioning accuracy of NavCom
developed GNSS hardware.

.. . . The StarFire correction stream consists of the RTG generated
GNSS precise orbit and clock values differenced with respect to the
GNSS broadcast ephemeris.

, , , The RTG code is the latest state of the art implementation from
NASA's Jet Propulsion Laboratory."

More on RTG:

http://gipsy.jpl.nasa.gov/igdg/system/od/index.html

Some older publications imply that JPL and NavCom (or John Deere --
think they were spun off once, then brought back) may have had a joint
venture at one time.

The world map in this 2004 paper shows roughly equal number of JPL and
NavCom reference stations (NavCom in green, the John Deere color):

http://www.gmat.unsw.edu.au/wang/jgp...2/v3n12p19.pdf

This 2001 NavCom press release (reprinted in GPS World) describes a
joint ventu

http://www.navcomtech.com/News/PressReleases.cfm?id=8