Re: Puzzled by >1 WAAS bird

Bitstring <4728B013.808DD03F@xxxxxxxxxxxxxxxxx>, from the wonderful person Jack Yeazel <jack@xxxxxxxxxxxxxxxxx> said


Dan Anderson wrote:

Jack Yeazel wrote:
> OK, in that example, the GPSmap 76Cx unit has SiRF, but the
> Vista HCx doesn't... We'll have to ask Allory (who now has
> the HCx) to see if it ever receives more than one WAAS
> Sat...

The HCx (MediaTek chipset) receives one WAAS satellite
at a time. Garmin chipsets can receive two WAAS
satellites at a time.

You are correct... Allory says his Vista HCx will only
receive one WAAS Sat at a time while his Venture Cx was
locked on to 48 and 51 the whole time...

I'd still like to know if the SIRF chipsets (which only seem to lock one Waas satellite at a time) really do, as I suspect, only lock them when the satellite is sending ranging data as well as correction data. That is the only explanation I have been able to come up with as to why the 60CX/CSX won't lock EGNOS satellites 90% of the time (EGNOS seems to put out ranging data relatively rarely).

--
GSV Three Minds in a Can
10,002 Km walked. 1,952 Km PROWs surveyed. 35.5% complete.
.

Relevant Pages

  • Re: WAAS differences between Garmins old and new units?
    ... It is generally true that Sirf does not use WAAS satellites for ranging data. ... None of the SiRF II designs show the satellite on the display although I can see it in GSA messages in a GlobalSat implementation but not GSV which would show its position. ...
    (sci.geo.satellite-nav)
  • Re: Puzzled by >1 WAAS bird
    ... > the HCx) to see if it ever receives more than one WAAS ... I'd still like to know if the SIRF chipsets (which only seem to lock one Waas satellite at a time) really do, as I suspect, only lock them when the satellite is sending ranging data as well as correction data. ... That is the only explanation I have been able to come up with as to why the 60CX/CSX won't lock EGNOS satellites 90% of the time. ...
    (sci.geo.satellite-nav)
  • Re: WAAS differences between Garmins old and new units?
    ... None of the SiRF II designs show the satellite on the display although I can see it in GSA messages in a GlobalSat implementation but not GSV which would show its position. ... If a GPSr is in a position to pick up 47 (or another WAAS satellite that is providing valid data) then it will update 35's ephemeris data; after that, if 35 is picked up again it will be shown in the new position and it's correctional data will be used. ... I think Garmin is dependent on SiRF to solve the problemwith WAAS processing. ...
    (sci.geo.satellite-nav)
  • GPS Tip: What is WAAS Ranging data?
    ... GPS Tip: What is WAAS Ranging data? ... If you live in the western half of the USA and have given up on WAAS ... satellite to be used as a GPS satellite. ...
    (sci.geo.satellite-nav)
  • Re: WAAS differences between Garmins old and new units?
    ... It is generally true that Sirf does not use WAAS satellites for ranging data. ... None of the SiRF II designs show the satellite on the display although I can see it in GSA messages in a GlobalSat implementation but not GSV which would show its position. ...
    (sci.geo.satellite-nav)