Hi,
On 08/01/14 16:33, ziggy9+time-n...@pumpkinbrook.com wrote:
I thought I had seen something regarding this before, and sure enough here it
is:
<http://www.freqelec.com/gps_gnss/waas_for_telecom_wp_5-06.pdf>
<http://hugofruehauf.com/pdf/24-WAAS_for_Telecom_2003-upd_2011.pdf>
<http://www.dtic.mil/dtic/tr/fulltext/u2/a485380.pdf>
All variations on the same idea - essentially point a DBS dish at a WAAS
satellite. Indications are that WAAS alone can be used for timing and the
articles specifically touch on GPS backup and jamming resistance. Each article
is a bit different so suggest reviewing all of them.
I guess it's an open question if your receiver can use WAAS alone for timing. I
don't have one to test with, but does anyone know if the LEA-6T supports this
mode? It would seem so.
Well, if you dip your nose into the WAAS specification
http://www.faa.gov/about/office_org/headquarters_offices/ato/service_units/techops/navservices/gnss/library/documents/media/waas/2892bC2a.pdf
You will find that it has messages holding it's own orbit (message type
9) as well as deviation from WAAS system time and UTC correction
parameters (message type 12).
Using a surveyed position, aiming an antenna at a WAAS bird and then
using a one-channel receiver should be achievable. A benefit of the WAAS
signal is that by directing a channel to a WAAS rather than a GPS bird,
you do not loose the navigation-contribution of that channel, but you
gain the additional correction material, thus doing so should be a net
gain with a rather small loss.
Anyway, I think looking at the actual signal spec gives better knowledge
than just looking at derivative work.
Cheers,
Magnus
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