Accuracy of home point

Gratton · Aug 30, 2020

How accurate do you find the home point? I was flying with 13 satellites and one of those orange circle landing pads that I just got. I took off from it, flew around for a bit and hit RTH. It was of by a couple of feet. I realize that's pretty good but it's it part for the MM?

Thanks,
Mikeg

dirkclod · Aug 30, 2020

Mines never really been dead on but never thought it would be.
Have except for a few times just took back over when it got over head and flew around come ing down for stick practice .

douglas_in_philly · Aug 30, 2020

The Mini is my first legit drone (had a $50 cheap-o without GPS about 4 years ago), and I never expected it to be able to land *exactly* in the spot from where it took off. I don't think GPS is *that* accurate to begin with--there's always a little variance (I think I read once that there are government/military GPS systems that *are* pinpoint accurate, but we don't get to use those). That said, my Mini comes down basically right from the spot where it took off--never more than a foot or two in any direction, I'd say.

old man mavic · Aug 30, 2020

as the MM does not have precision landing then anything within 5 ft of the landing is going to be pretty good the GPS is not that accurate
as DC said if you do a RTH then once you get about 10 ft from the ground just cancel and land it on the mat yourself ,it is good practice to get it in the center especially if it is a bit windy
and the more you do it the better you will get
as with any aircraft the two most critical parts of the flight, are take off and landing ,get those right and the rest is easy in comparison

diver dave · Aug 30, 2020

I was surprised the difference in precision landing my pal and i were getting with 2 drones, MM and MP, we both have one of each. His were spot on every time, mine were slightly off every time, just a few feet and no problem to correct. However, when he flew my drones they were spot on. We discovered that the pro particularly needs to raise up to 10 meters, and hover for a few seconds, so it can "see" the landing site i guess. We discovered that both drones were way better if we raised up a decent amount, 30 foot/10 mtr and hovered for 10 seconds or so. He was gently raising up, hovering whilst he checked things over and made sure all was well, i was raising up and and moving forward more or less at the same time. Now, its up, hover and then away and the precision landing and gps have the time to find out where take off point is.

Gratton · Aug 30, 2020

old man mavic said:
as the MM does not have precision landing then anything within 5 ft of the landing is going to be pretty good the GPS is not that accurate
as DC said if you do a RTH then once you get about 10 ft from the ground just cancel and land it on the mat yourself ,it is good practice to get it in the center especially if it is a bit windy
and the more you do it the better you will get
as with any aircraft the two most critical parts of the flight, are take off and landing ,get those right and the rest is easy in comparison

Yeah, that's what I generally do as well.

MikeG

shaneb50 · Aug 30, 2020

Even though the Mavic Mini doesn’t have accurate RTH . It still will land with in a couple of feet from it’s take off area.[emoji106]
And that’s pretty good enough to get you back home safely from it’s long flight [emoji574]️
I have been really impressed with the mini drone. And with most DJI drones they are great drones to have around.[emoji3][emoji574]️[emoji927]

Meta4 · Aug 30, 2020

Gratton said:
How accurate do you find the home point? It was of by a couple of feet. I realize that's pretty good but it's it part for the MM?

Your homepoint accuracy is the accuracy of consumer GPS.
It's not pinpoint accurate like some assume and has a variable inaccuracy.
If you tested 10 times, you might get 10 different points and most would be within 10 feet but it's even possible that sometimes it could be even more.

GPS.gov: GPS Accuracy

Information about GPS accuracy

www.gps.gov

The lesson is to choose a home point without obstacles nearby.

Lionfish · Aug 31, 2020

Meta4 said:
Your homepoint accuracy is the accuracy of consumer GPS.
It's not pinpoint accurate like some assume and has a variable inaccuracy.
If you tested 10 times, you might get 10 different points and most would be within 10 feet but it's even possible that sometimes it could be even more.

GPS.gov: GPS Accuracy

Information about GPS accuracy

www.gps.gov

The lesson is to choose a home point without obstacles nearby.

Interesting link thanks .

scro · Aug 31, 2020

@diver dave Did I understand you right that the Mini RTH accuracy is better if you first go straight up to around 10m and hover for ~10sec before heading off for your flight? Makes sense for larger mavics with precision landing, so they can capture the data needed to supplement GPS, but not quite what I'd expected for the mini.

I very rarely use the RTH so I've never really explored the accuracy of RTH or what affects it.

Dave Maine · Aug 31, 2020

There are 2 issues involved here.

GPS is the first. Using it alone without any help, 5-10 feet errors should be expected due to the accuracy of the GPS signal itself.

This is seamlessly augmented by using the downward vision sensors to build an image of the takeoff point so that this saved image can be compared with the real-time image being generated as the drone defends to land.

Acquiring the takeoff image requires a vertical takeoff and a hover around 10 feet for 10 sec for the drone to acquire an image accurate enough to be used for a precision landing.

Gratton · Aug 31, 2020

Dave Maine said:
There are 2 issues involved here.

GPS is the first. Using it alone without any help, 5-10 feet errors should be expected due to the accuracy of the GPS signal itself.

This is seamlessly augmented by using the downward vision sensors to build an image of the takeoff point so that this saved image can be compared with the real-time image being generated as the drone defends to land.

Acquiring the takeoff image requires a vertical takeoff and a hover around 10 feet for 10 sec for the drone to acquire an image accurate enough to be used for a precision landing.

I'll try the 10 second 10' hover. With that bright orange launch/ land pad, it should have a good image once it gets closer.

Thanks!
MikeG

Meta4 · Aug 31, 2020

Gratton said:
I'll try the 10 second 10' hover. With that bright orange launch/ land pad, it should have a good image once it gets closer.

If you are flying a Mavic Mini, it doesn't have the Precision Landing feature and isn't going to record any image.
Your RTH autolandings will only use GPS so there's no point waiting for an image that won't be taken.

If you had an Air 2, you'd have to wait at 7 metres (23 ft)

Redvers · Aug 31, 2020

Gratton said:
How accurate do you find the home point? I was flying with 13 satellites and one of those orange circle landing pads that I just got. I took off from it, flew around for a bit and hit RTH. It was of by a couple of feet. I realize that's pretty good but it's it part for the MM?

Thanks,
Mikeg

Sometimes my MA2 lands within couple of inches! Mostly within one foot. I calibrate the compass regularly

Meta4 · Aug 31, 2020

Redvers said:
Sometimes my MA2 lands within couple of inches! Mostly within one foot. I calibrate the compass regularly

The compass makes no difference to landing precision.
And if it's working properly, there's no need to recalibrate it, that won't improve anything.

Gratton · Aug 31, 2020

Meta4 said:
If you are flying a Mavic Mini, it doesn't have the Precision Landing feature and isn't going to record any image.
Your RTH autolandings will only use GPS so there's no point waiting for an image that won't be taken.

If you had an Air 2, you'd have to wait at 7 metres (23 ft)

I am flying the MM so I guess I'll have to be satisfied with what I've got for accuracy.

Don't get me wrong, I wasn't too upset about it, I just thought it was supposed to be dead on. Now I know better.

Thanks to everyone for the education!

mikeg

Gauts · Aug 31, 2020

I fly the MM as well and never got outside of 1 meter , very good if you ask me . It's the same on my boat , looking for a way point is never right on always misses by about a couple of meters . What I don't get is how you guys get like a dozen satellites at a time when I only pick up 5 or 6 on my MM or in my boat . I presume it's my location .

Dave Maine · Aug 31, 2020

Location, time of day, latitude. The GPS satellites are continuously moving, and dropping in and out of the solution for positioning. Any horizon interference will also contribute. Sounds as if you may be at sea, so that may not be relevant. If you are on a lake, then that may be part of the problem.

Gratton · Aug 31, 2020

Gauts said:
I fly the MM as well and never got outside of 1 meter , very good if you ask me . It's the same on my boat , looking for a way point is never right on always misses by about a couple of meters . What I don't get is how you guys get like a dozen satellites at a time when I only pick up 5 or 6 on my MM or in my boat . I presume it's my location .

I'm surprised, you're only an hour and a half north of me. 10 is a low number of satellites for me.

Mikeg

Meta4 · Aug 31, 2020

Gauts said:
I fly the MM as well and never got outside of 1 meter , very good if you ask me . It's the same on my boat , looking for a way point is never right on always misses by about a couple of meters . What I don't get is how you guys get like a dozen satellites at a time when I only pick up 5 or 6 on my MM or in my boat . I presume it's my location .

It's not your location.
Wherever you are in the world, there should always be more sats than you need.
I don't know which sats your boat GPS is using, perhaps it's an old machine and only uses US GPS sats?
That would mean it receives less than the Mavic but it should still be getting 9-10 almost all the time.

The Mavic also receives signal from Russian GLONASS sats so it can get >20 at a time depending on where the sats are.
The important thing is that your GPS antenna is out in the open and its skyview is not blocked by obstacles.

Accuracy of home point

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