Hi everyone,
I’m involved in a particular project in which I’m using an APM 2.8. For me the time spent in getting the GPS lock is so important. The first time I power up the APM 2.8 I get the GPS lock 1 minute later aproximately. The next time I get it in 25-30 segons. I would really need to decrease this time waste.
Is there any way to achieve what I need? Could anyone help me?
Thanks in advance!
Sergi
1 minute on a cold boot of the GPS is perfectly normal even for a high quality GPS. And 25 to 30 seconds on a warm boot is also perfectly normal. No time is being wasted.
Assuming you are using u-blox you can inject all the aiding messages to the GPS to download a database of the current ephemeris. You can download the predictions from the internet and send it via MAVLink, but it will require you to implement the protocol on the GCS side for it (as well as read the documentation on it).
Thank you so much for your answers!
WickedShell I didn’t have any idea about that. Could you please give me extra information about it? Or documentation link?
For the GCS and the Mavlink protocol there shouldn’t be any problem. I’m using them for this project. I’m sending the Mavlink protocol through a microcontroller to the APM.
Thank you so much for your help!
It’s documented in the u-blox protocol manual here: https://www.u-blox.com/sites/default/files/products/documents/u-blox8-M8_ReceiverDescrProtSpec_(UBX-13003221)_Public.pdf Note that the MGA stuff discussed inside that protocol manual is for u-blox 8 series and newer, the previous generations (6/7) used different messages for downloading the assistance data.
As far as the MAVLink side the data can just be injected with the http://mavlink.org/messages/common#GPS_INJECT_DATA message. If the message was larger then fit in that payload you could use GPS_RTCM_DATA however, that requires a much newer firmware.
I’m unsure if you will be able to use GPS_INJECT_DATA with Copter 3.2, it’s sufficiently old that I don’t know if that will just be supported or not.
Thank you so much! I’ll take a close look. I’ll tell here my experience and I’ll check compatibility issues you are talking about.
note, the injection thing that @WickedShell mentioned won’t work on the [very old] APM 2.8 hardware.
The reason a cold start on the GPS takes longer than a warm start is because the onboard battery has lost power and the GPS cannot hold the array information on it’s chip.If you power up the system regularly and allow the small button battery to recharge it can hold the array for a few days.Then when you connect up for flight you’ll get the fastest GPS lock possible.It’s as simple as that.A craft used regulalry doesn’t see this problem and finds GPS lock quickly.
If I leave one of my copters in the hangar for a few weeks it can take several minutes for the GPS to get going.