Help with SiRF IV

[ThomasH]

I am writing software that makes use of a BU353-S4 GPS receiver. The receiver uses a SiRF Star IV chip. I could use help understanding some details...

The xxGSV sentence transfers information of four satellites. xx being the "talker". Multiple sentences (up to three) are generated where the number of satellites in view exceed the sentence length.
Perhaps someone can tell me if the chip supports both GPGSV and GLGSV? My understanding is that all satellites in view are shown through the GPGSV. True? I have seen other software that makes distinction between the two talkers.

I know there is a conversion needed between NMEA ID and PRN. As I understand the conversion:
NMEA ID 1 to 32: GPS satellite, PRN = NMEA ID
NMEA ID 33 to 64: WAAS satellite, PRN = NMEA ID + 87
The current WAAS PRNs in use are

PRN - NMEA ID
133 - 46
135 - 48
138 - 51 Decommissioned
131 - 44

NMEA ID 65 to 96: GLONASS satellite, PRN = NMEA ID - 64
Is there a reference as to how other augmentation system satellites are mapped into NMEA?
Question is already answered. See:

GPSrChive - Satellites

The SiRF chip tracks up to 48 satellites. Why are only 12 reported by the GSV sentence?

Thanks for your help: Tom

 

[ThomasH]

I am writing software that makes use of a BU353-S4 GPS receiver. The receiver uses a SiRF Star IV chip. I could use help understanding some details...

The xxGSV sentence transfers information of four satellites. xx being the "talker". Multiple sentences (up to three) are generated where the number of satellites in view exceed the sentence length.
Perhaps someone can tell me if the chip supports both GPGSV and GLGSV? My understanding is that all satellites in view are shown through the GPGSV. True? I have seen other software that makes distinction between the two talkers.

I know there is a conversion needed between NMEA ID and PRN. As I understand the conversion:
NMEA ID 1 to 32: GPS satellite, PRN = NMEA ID
NMEA ID 33 to 64: WAAS satellite, PRN = NMEA ID + 87
The current WAAS PRNs in use are

PRN - NMEA ID
133 - 46
135 - 48
138 - 51 Decommissioned
131 - 44

NMEA ID 65 to 96: GLONASS satellite, PRN = NMEA ID - 64
Is there a reference as to how other augmentation system satellites are mapped into NMEA?
Question is already answered. See:

GPSrChive - Satellites

The SiRF chip tracks up to 48 satellites. Why are only 12 reported by the GSV sentence?

Thanks for your help: Tom

It's been a while since I wrote and I have continued to look for answers. In case there is interest I will post the answers found and to my best efforts are correct:

The SiRF Star IV chip is GPS only. Other GNSS constellations are not supported by this version of chip. I believe that there is a Star V chip that is or will be available. The ownership of the company has changed several times and the documentation for the part is closely held. For all NMEA based software, I have been using SiRF NMEA Reference Manual Rev 2.1 as downloaded. It is unclear if this is the exact documentation I should be using but details of revisions are not available to me. From all this I believe there is a single talker supported which is GPS. The prefix for all transmit and receive sentences is GP.

Since a single constellation of satellites is supported my software will use only the NMEA names. I was interested to find certain satellites that support SBAS were replaced. This is a topic I will dig into later.

Software I have written so far does just a few things:
- Interfaces over USB with the BU353-S4.
- Transmits commands to setup / reset the SiRF chip.
- Receive, validate and decode the NMEA sentences sent by the SiRF chip.
- Produce and display the fix along with a quality indication.
- Produce a "Destination fix" from a "Start position fix", a bearing and a distance. (Uses Haversine).
- Produce bearing and distance from a "Start position fix" and a "Destination fix".
- Take reduced bearing notation (survey) and produce both bearing and reverse bearing.

If there is interest I can provide the app.

-Tom