How many satellites needed to synch GPS' to fly

I bought two of 2450GPS. I noticed the second drone took much longer to synch than the first. Then I found on android app, it would need to lock on 10 satellites to claim the GPS lock (green LED steady). Is it true and fixed in design?

The minimum number of satellites to lock is 6, but it also uses a number of other quality metrics, including GPS velocity accuracy, GPS horizontal accuracy etc.
It will get GPS lock much faster if you connect with the app first (or the status interface of the web interface), as the app will download both the time and a block of GPS assistance data to the drone which reduces the lock time a great deal.
You can fly without GPS lock (in indoor mode), but if you want to fly with GPS lock then it does need a high quality GPS lock otherwise it would fly very badly.
Cheers, Tridge

For really detailed information see this guide here:

That is a guide I wrote for internal use in SkyRocket, but there is no reason I shouldn’t share it. It gives you some more detailed information on the process of getting good GPS lock on this vehicle.
Cheers, Tridge

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Thanks Tridge! Very informative doc. What I want to fly 2450GPS with QGroundControl, so accurate GPS information is critic.

This works fine and I get a lock pretty quickly when I do use the app, but I often want to fly waypoints via tower or some other GCS and don’t need the viewer for anything but the GPS data. I’ve noticed I have to connect with the app even when I just change batteries of it takes forever to get a fix. Is there any reason not to cache the assistance data on the CF card if it is present and reload it from there on power up? (Just took a second look at the document it it seems this may already be planned) For that matter, is there any reason to require the app at all? Can’t we store the data the GPS would have saved itself if it had a battery and fall back to the normal “first fix takes longer” behavior if we don’t run the app? Of course, this is of more use to developers than the average customer so I understand if it’s not a priority.


Perhaps the caching of GPS data on the CF card from the last app connection has already been implemented? Turns out I didn’t have the CF card inserted like I thought I did the last time I flew.

yes, it caches the GPS offline correction data on the microSD, and will even cache it in flash if a microSD isn’t available.
That data is useless without the correct time though. It does cache the time, and if you don’t get an external source of time then it assumes that two minutes have gone past since the last time the cache was updated (rough battery change and new flight time).
So you need to connect either the web UI or the app in order for it to get the time, so it knows what part of the offline GPS data it should use.