Garmin Satelite Numbering System

[+Alfresco2006]

Can anyone tell me how Garmin numbers GPS satelites. They appear to use a number system of there own as the satelite numbers as I see them on my unit not only do not correspond to SVN's etc but they also differ from a friends Lowrance unit. He gets satelite 31 up here and I don't, I get 51 which appears to be the same as his 31 which is a recently new online satelite.

[+Timpat]

Can anyone tell me how Garmin numbers GPS satelites.

They subtract 87 from the satellite PRN number. So our WAAS bird #51 has the PRN number 138. Can't tell you why, but this is what they do.

[+PDOP's]

...and for the regular satellites Garmin (and everyone else) use the PRN number. Teamtrailwalker has a nice summary here.

[shivia]

They subtract 87 from the satellite PRN number. So our WAAS bird #51 has the PRN number 138. Can't tell you why, but this is what they do.

- rookie's question...what does mean "PRN"? thanks.

[+Timpat]

Pseudo-Random Noise (PRN).

 

From the Satellite Navigation & Positioning Laboratory. "A binary signal with random noise-like properties. It is generated by mathematical algorithm or "code", and consists of repeated pattern of 1's and 0's. This binary code can be modulated on the GPS carrier waves using Binary Shift-Key (BSK) modulation. The C/A-Code and the P-Code are examples of PRN codes. Each satellite transmits a unique C/A-Code and P-Code sequence (on the same L1 and L2 frequencies), and hence a satellite may be identified according to its "PRN number", e.g. PRN2 or PRN14 are particular GPS satellites."