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3D fix 3 satelites

I have just been testing my GPS as it takes me ten minutes to get a 3d fix? so I decided to see what is going on, and yes it takes ten minutes still, but it indicates a 3d fix and sat count 3? this I thought is impossible? you need at least 4 sats for a 3dfix? after 18 minutes 4 sats and 20 minutes 5 sats 21 minutes 6 sats this is being tested outside I have tested with and without receiver connections and taking the board out of the Tricopter and getting the same results. Surely this cant be right for a gps that claims a lock in under a minute?

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Replies

  • I have a similar problem. I have been testing my APM2 with the MediaTek GPS and the first time out the box the GPS took in the order of 45 minutes to download the almanac and get a fix. I thought maybe it's because I am in the Southern hemisphere that it takes longer. I left it running the whole day to make sure it catured the almanac properly. But then I powered it down and the next day it took about 15 minutes to get a fix. The blue LED was solid on, but the GPS status on the Mission Planner still said status 1 (no-fix). I tried again with only a short power down of a few seconds and it took another 10-15 minutes or so get a fix again. It seems like the almanac is not being stored.

  • You need 4 sats for a 3D fix.  The first time out of the box should take perhaps 12-15 minutes to download almanac data from the sats.  After that it should take only a minute or two for a fix.

    The DIY Drones "custom" firmware cripples some of the MediaTek GPS chipset functions, like saving your settings.  Maybe it is also failing to save the almanac data.  I'm also not sure if it's maintaining the empheris data either, so it probably requires a cold start each time you power it up.

    I don't think it's losing the almanac data though, since my unit locks after a few minutes.  Something must be wrong with your unit.

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