RTH accuracy

[RayTerry]

After I calibrate the compass on my P3S, the RTH accuracy is about 2'. After a number of flights from the same site and over several weeks, the accuracy gets worse, up to 20' I have to go to S1 to keep it from landing in a tree. After I calibrate the compass again, the accuracy is back to 2'. Is this normal?

 

[Steve7777]

After I calibrate the compass on my P3S, the RTH accuracy is about 2'. After a number of flights from the same site and over several weeks, the accuracy gets worse, up to 20' I have to go to S1 to keep it from landing in a tree. After I calibrate the compass again, the accuracy is back to 2'. Is this normal?

I think you posted this yesterday here:- RTH problem

I agree with the person who responded on the other thread. 2' is exceptional accuracy for GPS and (although I don't know how many times you've observed it happening) the better location accuracy is maybe just coincidence.

 

[Meta4]

After I calibrate the compass on my P3S, the RTH accuracy is about 2'. After a number of flights from the same site and over several weeks, the accuracy gets worse, up to 20' I have to go to S1 to keep it from landing in a tree. After I calibrate the compass again, the accuracy is back to 2'. Is this normal?

There is nothing you can calibrate that would have any effect on RTH landing precision.
It's completely unrelated to the compass.
Consumer GPS accuracy is variable.
Much of the time it will be within 2 metres but occasionally it will be even further away and that's completely normal.

You don't need GPS to land your Phantom though.
You can cancel RTH anytime (if you have signal) and resume control and land wherever you choose.
Or if you really want precise RTH autolanding, get a P4 pro and use the Precision Landing feature which uses optical technology to land within an inch every time.

 

[RayTerry]

There is nothing you can calibrate that would have any effect on RTH landing precision.
It's completely unrelated to the compass.
Consumer GPS accuracy is variable.
Much of the time it will be within 2 metres but occasionally it will be even further away and that's completely normal.

You don't need GPS to land your Phantom though.
You can cancel RTH anytime (if you have signal) and resume control and land wherever you choose.
Or if you really want precise RTH autolanding, get a P4 pro and use the Precision Landing feature which uses optical technology to land within an inch every time.

 

[RayTerry]

Why does DJI say you should calibrate the compass when you move to a new location?

 

[With The Birds]

Why does DJI say you should calibrate the compass when you move to a new location?

They have stopped saying that.....

 

[msinger]

Why does DJI say you should calibrate the compass when you move to a new location?

I'm not sure why DJI continues to recommend this. The last time I saw it recommended was in this article from December 21st.

For better advice, check out the Compass Calibration Guide.

 

[Meta4]

Why does DJI say you should calibrate the compass when you move to a new location?

This is what DJI say these days in up-to-date manuals:

DJI is not great at communicating and they have people that recycle old stuff without understanding details.

Your compass has no effect on GPS accuracy anyway.
They are completely separate systems.

 

[RunningWithScissors]

After I calibrate the compass on my P3S, the RTH accuracy is about 2'.

As stated by others, if you're getting GPS accuracy of 2' on a regular basis, consider yourself very fortunate. Current civilian GPS accuracy is quoted @ 4 meters, maybe 3 meters on a good day. That's expected to improve to 1 meter once GPS III is fully operational. UntIl then, anything significantly better than the current accuracy is a plus.

 

[AndrewCCM]

I agree about GPS accuracy. That is one improvement they have made with P4.. The downward sensors give an extra set of eyes/parameters to guide the RTH with more precision. With my P4P, RTH returns back on my landing pad within a foot or so every time. GPS alone would be much less accurate I’d think.

 

[Just_nick]

Don't expect pinpoint accuracy from a P3S. Expect it to land somewhere in the vicinity of where you started, and I would personally just land it myself after using RTH to bring it back.

 

[BillyBottle]

I think the question is-
How come the accuracy can be seemingly restored to **** close, but then drift off over time? And yet be restored and drift off again ...and again... and again...?

 

[Steve7777]

I think the question is-
How come the accuracy can be seemingly restored to **** close, but then drift off over time? And yet be restored and drift off again ...and again... and again...?

And the answer from several here has been 'Who knows?'.... There is no connection between compass calibration and GPS accuracy...

So it's still a mystery....

 

[RayTerry]

And the answer from several here has been 'Who knows?'.... There is no connection between compass calibration and GPS accuracy...

So it's still a mystery....

 

[RayTerry]

I originated this thread. I am now convinced that RTH is by GPS and the compass has nothing to do with it. My conclusion re. the RTH drifting off then being restored after calibration the compass is that it was a coincidence.

 

[Steve7777]

I originated this thread. I am now convinced that RTH is by GPS and the compass has nothing to do with it. My conclusion re. the RTH drifting off then being restored after calibration the compass is that it was a coincidence.

I think that's probably a correct conclusion, Ray....

 

[Meta4]

I think the question is-
How come the accuracy can be seemingly restored to **** close, but then drift off over time? And yet be restored and drift off again ...and again... and again...?

The accuracy isn't "restored".
As mentioned in post #3 GPS has variable accuracy that gives random small errors.
Here's a plot of the positions recorded by a fixed GPS unit over two hours. (Source: Calculating your own GPS accuracy)

For more info on GPS (in)accuracy, read: GPS.gov: GPS Accuracy

 

[RayTerry]

I am well aware of the inaccuracy of GPS. I take off in a tight space. If the RTH is off more than 15' I'd either be in a tree or in the Chesapeake Bay. Fortunately I have S1 and I know how to fly a drone.

 

[jbwill]

I flew yesterday, had good accuracy (3ft) on a cell phone real estate app. I use Beginners Mode with a P3P to lessen a chance of a fly away (this is my 3rd AC). First location no problems, 2nd location wife was talking & I don't remember hearing Home Pt updated. As soon as I was about 3 ft up, the AC immediately flew backwards toward the area of the previous home point. I was able to stop it from going further, but sticks were not going where I told it to & it would not hover, kept moving around.

Recovered & on 2nd flight it did record home point, flew with no problem 3 more times from different locations.

I was curious if GPS was whacky, so I used my phone app that I used earlier & it went to 20ft.

Thought this might fit in this thread, if not move appropriate spot or advise me where to put it.

Thanx to all contributors, this forum is priceless!

 

[Meta4]

As soon as I was about 3 ft up, the AC immediately flew backwards toward the area of the previous home point. I was able to stop it from going further, but sticks were not going where I told it to & it would not hover, kept moving around.

I was curious if GPS was whacky, so I used my phone app that I used earlier & it went to 20ft.

Your post is a little confusing and what happened isn't very clear.
Disorientation is possibly a factor.
If you have any mysterious flight incidents, you can always look into the recorded flight data to find out what ahppened.
To do that, go to DJI Flight Log Viewer
Follow the instructions there to upload your flight record from your phone or tablet.
If you need help with analysis, come back and post a link to the report it provides and someone might be able to give you an understanding of the cause of the incident.