Turning on SiRF STAR IV GSD4e capabilities

[ThomasH]

Hi,

I believe that my GPS is WAAS/EGNOS capable. Does the SiRF chip need initialization to use this? I am asking because I receive the following message:
$GPGGA,<time>,<Latitude>,N,<Longitude>,W,1,08,0.9,369.4,M,-35.0,M,,0000*6B

This give me a position fix indication of 1 which is: GPS SPS Mode, fix valid

I had hoped/expected to see fix indication of 2 which is: Differential GPS, SPS Mode, fix valid

Am I misunderstanding that WAAS is "Differential"?
Are there more setup strings the chip needs to boost accuracy?

Thanks -Tom

 

[Nuvi-Nebie]

You will only get an indication of a WAAS satellite if one is visible to your GPS, the WAAS / EGNOS (SBAS) satellites are geostationary I.e. they are always in the same place in the sky, they are above the equator so from Canada the WAAS satellites will be in the south, if your view if the southern sky is obsured you won't 'see' one

 

[ThomasH]

Thank you for your help and info. I believe (please confirm) that the three satellites from your map are PRN-133, PRN-135 and PRN-138. Information from a wiki suggests another source: PRN-131. This is Eutelsat 117 West B. Is this a valid WAAS source?

There is also an entries that I don't understand for satellites 28, 31 and 32. I take it that these are not broadcasting WAAS info?

-Tom

 

[Nuvi-Nebie]

There is a link here that details the satellites: -
http://gpsrchive.com/Shared/Satellites/Satellites.html#Track%
Note that some GPS receivers use NMEA numbers and some PRN. numbers, 1 - 32 NMEA/PRN are GPS (USA) satellites, NMEA 33 - 51 PRN 120 - 138 are SBAS (WAAS / EGNOS)

So PRN 131 is WAAS and NMEA/PRN 28,31 and 32 are not

 

[ThomasH]

Thank you for the share of that link. Much information I wasn't aware of, a very good read.

-Tom

 

[leejohn63]

thank you for sharing the ink, much appreciated sir