New here, have a question about GPS

[CharlieR]

Hey guys! New to this forum. I have a question about GPS.

I know that multirotors like the Phantom can hover in a set position really accurately through GPS, but according to the Internet, GPS tends to be a few meters off!

Of course, this may not be correct, but how do drones like the Phantom and the Mavic hover so accurately?

Thanks in advance.

 

[Craftydan]

A few feet off of what?

The real point in space or where you just left your quad?

Here's the trick: GPS error can be fairly big, but the error doesn't change rapidly.

So if you take-off at a measured point X/Y, fly around for a few minutes then use the same GPS to navigate back to the measured point X/Y, the quad won't land far from it's launch. Go back and look at the logs in Google earth and it might all be shifted off by a meter or 3, but as far as when you're flying, traveling between points your GPS just measured, or holding station at a measured spot is scary accurate.

The absolute error can also be corrected, depending on the data you have available, to sub-meter precision (sub-cm is also possible, but on a moving platform? that's usually done with long dwells on a nearby base station). Not sure if the Naza class controllers are using that or not, since the availability of regional corrections vary wildly.

It is also worth mentioning that the latest DJI products are augmenting GPS with optical ground-truthing sensors to reduce the impact of GPS error. The GPS still is the primary navigation sensor, but step indoors with your drone (or outside on a bad day) and the position hold isn't crippled by a poor/bad GPS fix.

BTW, Welcome to the forum!