mavic 2 GPS vs Phantom 3S

[ruggb]

I had a Phantom 3S. When it did an RTH the landing was almost always within 1m of takeoff point. That is by GPS location only.
My new M2Z only lands on my 1/2m pad maybe 50% of the time. I have very carefully calibrated IMU & compass several times to make sure I got it right. When I takeoff, I hover for a photo op. When it arrives at "home" (@200ft) it is not over the landing pad. Sometimes it is off by 4-5m or more. At that distance it can't photo correct when it get to ground level. If it is off only 1-2m it does photo correct at about 5m and then lands on the pad.

Both were flying in the same location.
If the Phantom GPS alone brought it down on target, what is wrong with the M2Z GPS?

 

[sas8888]

When you take off how high do you go for the photo and how long do you wait?

 

[ruggb]

the last time I waited 10 sec at takeoff height and then 10 sec at about 5m.
usually I just do the 5m one. BUT....it is correcting when it gets close enough via GPS. The problem is the GPS not the PL.
I must make sure I am well clear of trees on takeoff or else it may try to come down thru a tree.
Without PL it should act like my Phanton, but it does not. Maybe inherent in the options for antenna placement. The P3S was located on its leg.

 

[Mr. Salty]

How far away from the home point are you flying it before you hit RTH? Not altitude but horizontal distance.

 

[ruggb]

I have tried different distances. I haven't related distance vs rth accuracy. Do you have an idea about that?

 

[sas8888]

I Have done different heights experimenting and found the sweet spot at 10 to 12 meters up. Less than that and it was anywhere from 2 to 5 meters off on the return to home.
Also on the rth it flies back to general area and then as descending it starts to make its corrections closer you get to ground. You are correct that taking off between obstacles could cause disaster on landing.

 

[Former Member]

Many of the M2's I fly do the same thing. They get to near the home point, then start descending. They can be as you said, a foot or two away from the final landing point on their descent. Thats why I always gimbal straight down and see where the LZ will be in the crosshairs. I correct it manually so it avoids obstacles on the way down.

OP, youre not crazy. It does happen.

 

[ruggb]

is it a GPS issue? why did the P3S GPS seems more accurate? I mean I am talking a lot more than 2-3 ft. That would be the same as the P3S.

 

[Former Member]

is it a GPS issue? why did the P3S GPS seems more accurate? I mean I am talking a lot more than 2-3 ft. That would be the same as the P3S.

Are you using auto-takeoff?

 

[ruggb]

most of the time using auto takeoff
same as when I had the Phantom

 

[Former Member]

Are you using the latest firmware and dji go 4 app?

 

[ruggb]

yes - i think it is .400 now

 

[Former Member]

yes - i think it is .400 now

One of the recent updates included precision landing for the 2

 

[ruggb]

PL is obviously functioning if it corrects at 5 meters, right?
However, if it comes down to 5 meters 10 meters off there will be no match to the photo data below it and it tends to sit there scratching its toes. "Now what do I do"
BTW, that update came out a while ago maybe even in Dec 18

 

[Former Member]

If you cant get it to work the way you want it to, just gimbal down and match the grid crosshairs to the center of your LZ.

 

[sar104]

the last time I waited 10 sec at takeoff height and then 10 sec at about 5m.
usually I just do the 5m one. BUT....it is correcting when it gets close enough via GPS. The problem is the GPS not the PL.
I must make sure I am well clear of trees on takeoff or else it may try to come down thru a tree.
Without PL it should act like my Phanton, but it does not. Maybe inherent in the options for antenna placement. The P3S was located on its leg.

Have you thought of consulting the manual?

Precision Landing​

​

The Mavic 2 Pro/Zoom automatically scans and attempts to match the terrain features underneath during Return to Home. When the current terrain matches Home Point terrain, the Mavic 2 Pro/Zoomwill start landing. The DJI GO 4 app will show a terrain feature mismatch prompt if matching fails.​

​

Precision Landing performance is subject to the following conditions:​

a. The Home Point must be recorded upon takeoff and must not be changed during flight,​

otherwise the aircraft will have no record of the Home Point’s terrain features.
b. During takeoff the aircraft must ascend vertically 7 m before moving horizontally.​

c. The Home Point terrain features must remain largely unchanged.
d. The Home Point terrain features must be sufficiently distinctive.
e. The lighting conditions must not be too light or too dark.​

The following actions are available during Precision Landing:​

a. Throttle down to accelerate landing.​

b. Move the control sticks in any other direction to stop Precision Landing. The Mavic 2 Pro/ Zoom will descend vertically after the control sticks are released.​

 

[Former Member]

Have you thought of consulting the manual?

Precision Landing​

​

The Mavic 2 Pro/Zoom automatically scans and attempts to match the terrain features underneath during Return to Home. When the current terrain matches Home Point terrain, the Mavic 2 Pro/Zoomwill start landing. The DJI GO 4 app will show a terrain feature mismatch prompt if matching fails.​

​

Precision Landing performance is subject to the following conditions:​

​

a. The Home Point must be recorded upon takeoff and must not be changed during flight,​

otherwise the aircraft will have no record of the Home Point’s terrain features.​

b. During takeoff the aircraft must ascend vertically 7 m before moving horizontally.​

c. The Home Point terrain features must remain largely unchanged.​

d. The Home Point terrain features must be sufficiently distinctive.​

e. The lighting conditions must not be too light or too dark.​

​

The following actions are available during Precision Landing:​

​

a. Throttle down to accelerate landing.​

b. Move the control sticks in any other direction to stop Precision Landing. The Mavic 2 Pro/ Zoom will descend vertically after the control sticks are released.​

So, on the M2, during autotakeoff, it wont automatically enable precision landing? I know its not a choice, as it was on the MP. On the MP, you can select PL during autotakeoff.

 

[ruggb]

"Have you thought of consulting the manual?"

Have you thought of being less condescending?
I have read the manual and viewed videos till my monitor shut down.

It seems like everyone wants to tell me about PL. LET ME MAKE IT CLEAR. MY PL WORKS IF THE GPS GETS IT WITHIN RANGE OF THE PL. The problem appears to be that the GPS accuracy is not as good as the P3S was.

PL does not compare images at 200 ft. At that point it should be within a 5ft circle of the home point. My P3S was, the M2 is hit or miss.

Being 15-20ft horizontal of home point is not going to get it even close to a PL.

I have not tried it without PL. Next flight I will and will report how far off the GPS is. Maybe it will work better that way.

 

[Meta4]

I had a Phantom 3S. When it did an RTH the landing was almost always within 1m of takeoff point. That is by GPS location only.

The problem appears to be that the GPS accuracy is not as good as the P3S was.

For a start, your idea about the accuracy of the P3S isn't realistic and it seems your idea about GPS accuracy in general isn't correct.
GPS, any GPS is not pinpoint accurate and its inaccuracy will be variable.
Most of the time (under good conditions) it will give a position fix within 2 metres but sometimes it will be even be outside that.
Your P3S could not consistently perform an RTH landing within 1 metre, as the GPS equipment is not capable of that degree of accuracy.

Your Mavic 2 should be capable of similar GPS accuracy to any P3 and if you really believe it isn't, you need to look at the recorded flight data to see if there really is an issue and what might be causing it.

And finally, the autolanding following RTH is just a gimmick anyway, rather than an important feature.
A human should be able to cancel RTH and land properly every time.

 

[ruggb]

thanks Meta

As I said, my major concern is not the precision landing, as it appears to be capable of that and if I go higher on takeoff to get data it appears to work better. I get that.
Why the GPS doesn't bring it closer to vertical is my concern because it may have contributed to a tree landing in the past.

I just need to figure out how to verify the GPS is performing as intended and doesn't have some subtle problem. My P3S had a video transmission problem that took me almost a year to define and convince DJI it was there and I just barely got it fixed in warranty.