Hi, all -
I'm trying to use an array of 28 AudioMoth Dev units with GPS+GLONASS modules to capture 12-hour continuous recordings using the GPS-Sync firmware.
What I am finding is that the recorders get their initial fix (on being switched on) very quickly, and the first recording in the program is typically successful in both getting a fix and recording until the maximum file length. After that, however, most attempts to record - both continuing on during that initial recording session, and on subsequent days - fail because a GPS fix is never acquired. All recorders do not fail all of the time, but most recorders fail most of the time.
I have tried giving the recorders 900 seconds to get a fix (recordingFixDuration: 900) but this hasn't helped. And I've noted that when the recorders are first switched on, they do acquire a fix quickly, typically within 30s. I have also tried breaking the recording period into shorter recordings (ranging from 15 minutes to 1.5 hours) with breaks in between to allow more time for acquiring a GPS fix; this hasn't resolved the issue either.
If there is something else I should try to correct the GPS issue I would love to hear ideas. Alternatively I am wondering if it is possible to program the units to carry on recording (and saving the recordings) even if a fix isn't acquired? That way I would at least have the recordings even though I won't be able to sync them.
Thanks for any help and ideas!
Cheers, Laura
Hi,
Can you share the configuration that you are using. The AudioMoth-GPS-Sync firmware needs to have a continuous fix in order record the necessary PPS time signal alongside the WAV file.
In the case where the later recordings are successful, can you check the voltage in the WAV file. The GPS takes quite a lot of power when running continuously so I wonder if the batteries are running down which is affecting the ability of the GPS module to get a fix. What make and model of battery are you using? Also, what make and model of SD card are you using?
How accurate do you need the synchronisation to be? The AudioMoth-GPS-Sync firmware will synchronise to about 1us which is much better than required. If you use the standard firmware and use the GPS on either side of 1-hour recordings, then the synchronisation will typically be to within a couple of milliseconds which is good for most application. In the case that the GPS does not acquire a fix the recording will still be present and can be synchronised, with a bit less accuracy.
https://github.com/OpenAcousticDevices/Application-Notes/blob/master/New_Support_for_GPS_Synchronisation_in_the_Standard_Firmware/New_Support_for_GPS_Synchronisation_in_the_Standard_Firmware.pdf What type of environment are the devices deployed in?
Alex