NMEA questions

balloni55 shared this question 2 years ago

Hello menion,

hope you have had nice vacation and you are well recovered for new tasks ;-)


1. how did locus calculate "used sats" ? in example GGA and GSA are 10 used, locus display 15

2. why display locus 26 available sats ? in GSV sum total =24

3. when i record nmea while track recording locus always save 2 files, the second only contain a few bytes with last sentence, why?

4. is the accuracy calculated by locus and if, how is it calculated?


Comments (1)


Hello balloni,

yes, vacation was fine, little rainy but fine :)

I won't have positive answer for you in this case ... I do not know :).

If you use internal GPS and just recording nmea messages to file, then Locus use two completely independent systems. First one receive already computed data from Android system and display them to you ( like coordinates & satellites ) and second received NMEA messages. If you have enabled recording of nmea messages in settings, then Locus just save these messages into file without touching and using them.

So it may be even possible that these values does not match perfectly.

As I see, in NMEA are missing sats 33 and 38, so last two from US GPS source. I really do not know, maybe in NMEA message is one step behind/before what you see in skyplot.

Used sats are counted in case of available SRN value ( fourth number, so it's 30, 26, 20 ... ), when this value is missing, sat is not used.

3. about saved small file ... hmm did not noticed. Seems that you are using "separate_nmea_records" config.cfg parameter set to true? Consider as fixed.

4. accuracy, as I told before, it is received directly from Android system

Hope I gave you some answers, feel free to ask if something is not clear.