P3S GPS issue!

[betabilly]

Is the P3 Standard's GPS normally this prone to loosing satellite lock at ground level? Here's a couple examples I've experienced:

After having landed in an open field, I can walk over my aircraft and as I reach down to turn off the battery, I can hear my Go app say "Atti mode" and when I look down at the screen there's 7 satellites indicated. When I move my hand away from the aircraft, it cleverly goes back into P-GPS mode while still showing 7 satellites. Once in the air there's no problems with the aircraft inadvertently switching flight modes.

At times before taking off, the GO app will indicate 6 satellites acquired but even after waiting 3 more minutes will not have switched into P-GPS mode. Power cycling the app, remote and aircraft usually corrects this issue.

I never had this problem when I flew using the latest Android GO app on my tablet or the previous iOS GO app in conjunction with 1.8.10 firmware.

After I had updated the iOS GO app on my iPhone 6S-Plus to 3.1.15 and the firmware to 1.9.20 the issue first appeared. Reinstalled the app from the App Store and it made no difference. Once in the air, the aircraft flies just as well as it before the upgrades.

I don't know if the upgrades are to blame or should I go shopping for a new GPS module.

 

[Meta4]

Is the P3 Standard's GPS normally this prone to loosing satellite lock at ground level? Here's a couple examples I've experienced:

After having landed in an open field, I can walk over my aircraft and as I reach down to turn off the battery, I can hear my Go app say "Atti mode" and when I look down at the screen there's 7 satellites indicated. When I move my hand away from the aircraft, it cleverly goes back into P-GPS mode while still showing 7 satellites. Once in the air there's no problems with the aircraft inadvertently switching flight modes.

The number of sats your GPS receives is related to how much of the sky it has a clear view of.
The app should have no effect at all on this - it just shows you how many sats the GPS receiver finds.
You can block GPS signal by putting a hand on the top of the Phantom, trees or buildings around you can block some of the sky and a sat or two.
Once up in the air with a clear view of all the sky you should have no GPS problems.

 

[solentlife]

GPS signal is actually a very weak signal from that orbiting satellite ... a lot weaker than people imagine.

Its a strange thing that you can receive sats inside a GRP boat for example - but not inside an RV (there will be exceptions of course).

It would be unusual for a 'hand' to block sats - but a full body could well do. Once a receiver is on the ground - its field of view becomes limited and anything that walks up to it ... lies in its FoV will have an effect.
A persons body is mostly water - a strong inhibitor of RF ...

It would be interesting to know what would be the sat count if the AC was placed on a plastic picnic table of the ground at the location OP reports...

Nigel

 

[Meta4]

Its a strange thing that you can receive sats inside a GRP boat for example - but not inside an RV

It will be a simple matter of what is between the GPS antenna and the satellites.
Glass fibre and resin are like the plastic Phantom shell - transparent to the radio signal.
If there's aluminium insulation foil, other metal items, a steel boat hull etc, that can block signal.

It would be unusual for a 'hand' to block sats - but a full body could well do.

It's easy to test for yourself. You can block GPS signal by just placing a hand over the top of the Phantom.

It would be interesting to know what would be the sat count if the AC was placed on a plastic picnic table of the ground at the location OP reports...

In open, flat country, raising the Phantom a metre or two whould make next to no difference

 

[betabilly]

Thanks for all the plausible responses people, yet it's funny I never noticed this before and I've been flying Standards for 10 months. Maybe the solar activity is having some effect or I'm just getting on in age.

 

[N017RW]

Like solentlife said, the GPS signal at the Earth's surface/your quad's receiver is very weak, small, etc.
Somewhere around -150dBW, give or take.

There are on-line converters.
Using them results in a signal strength of: 1e-12 mW or, wait for it...

0.0000000000001 mW, or 0.0000000000000001 watts.

Easy to see how a hand could attenuate such a signal!

 

[Gryphon]

My Phantom is my second quad with GPS and placing a hand on top has the same effect on both. I can watch the sats drop out and then reappear as soon as i remove it.