Empty NMEA strings


I am flying multiple M2 devices on drones and using them for primary navigation. Every now and then I see a message that is basically empty like this:

$GPRMC, , , , , , , , , , , ,* 4B (without spaces between the commas, but the forum formatter turns that into a single comma)

The drone squawks that it received bad data and then immediately goes back to good.

I often notice these messages when the drone is sitting on the ground and isn’t maneuvering, so loss of signal isn’t from motion. In fact, the GGA message i received 0.2 seconds prior showed it was tracking 24 satellites, so something strange is going on.

Any ideas on:
(1) how can these messages can be prevented?
(2) can something be configured so they don’t appear even if there is a signal loss? I would rather have no message than an empty one
(3) Since these dropouts typically occur for only one cycle (while running at 5Hz), it seems like maybe this is more of a software/firmware issue than a real drop…any other reports of this?

Thanks. BTW, I am running FW version 31.8.


Hi @Keithb,

My apologies for the radio silence here.

Did I understand correctly that the empty GPRMC message occurs when M2 suffers from signal loss due to interference? If you set the rate to 1 Hz, do you see the same empty message?

To disable the RMC message, go to GNSS settings > Position Streaming, choose the NMEA format, and then disable the RMC message.

Hi @ruth.bongon ,

My configuration requires GGA and RMC messages at 5 Hz and those are the only NMEA messages that are selected for output. The problem occurs rarely but for reasons I don’t know. Typically this only occurs for one cycle and effects both message types.

When this occurs typically GPS quality is very good, and the example I gave above occurred when the previous messages (0.2 seconds prior) were showing the M2 was tracking 24 satellites…immediately after the blank message, normal data resumed. The system was sitting on the ground at the time as well, so it wasn’t caused by drone motion.

If the M2 looses track for some reason, is the empty message what would be expected? Is there any way to configure the M2 so that it sends nothing if signal is lost?


Hi @Keithb,

Apologies for the delay. I’ll discuss your case with the developers. Could you please share the Full System report of your device and the approximate time and date when the issue occurred?

Since the report contains sensitive data, you can send it to us via email at support@emlid.com. Thank you!