My HOMEPOINT position (H) in DJI Go app shows me in wrong place, normal ?

[KONY]

Hi,

After watching a scary video on youtube where a guy crashed his MAVIC into the ocean because (taking off from a hotel balcony) he didn't leave enought time for MAVIC to record the HOMEPOINT location after taking off, i decided to look at this subject more closely on my today's flight.

I started the MAVIC's rotors, heard the robotic female voice "homepoint has been recorded". Ready to take off. But just before taking off i checked the map on DJI GO app and to my surprise it was putting me in the middle of the water (check the H on attached pic).

But i was standing on the rooftop of my tower located a bit off that water (where it's written "south district office" on the top side on attached picture.)

So what does that mean ? does that mean that if i lose connection, and RTH is activated, then the MAVIC will land on water ?

Then it's problematic ! I then tried to click on that round compass circle on the MAP picture and click on the MAVIC Icon or Person's Icon thinking it would update more precisely but the H stayed there in the water...

Lastly the GPS of my phone was switched ON, and i had data connection...if ever that matters

any input ?

 

[msinger]

does that mean that if i lose connection, and RTH is activated, then the MAVIC will land on water ?

Yes.

Lastly the GPS of my phone was switched ON, and i had data connection...if ever that matters

It does not since the Mavic uses its internal GPS receiver when marking the home point on startup.

Are you able to reproduce this issue?

 

[KONY]

hi Msinger

what do u mean by reproduce the issue ? that was just taken 1 hour back...now it's dark outside so if necesary i'll try again tomorrow.

But according to you what could have have caused that misplacement on the internal DJI GO MAP?

 

[msinger]

what do u mean by reproduce the issue ?

Does it happen every time you start the motors?

You don't need to fly it to check. Head outside, fire up the motors, and see where the home point is marked.

what could have have caused that misplacement on the internal DJI GO MAP?

Check your TXT flight log to see if there were any GPS related errors. You can upload and view it here.

 

[John Shaw]

That's where the Mavic thinks you are. That looks to be about 120 meters on Google Earth. It's not that unusual to see that type of error before the GPS refines it's position. I would expect you might have to pause and reset home when it improves unless there is interference for the buildings.

 

[msinger]

It's not that unusual to see that type of error before the GPS refines it's position.

I think it's highly unusual. Perhaps the flight log will explain what happened.

 

[KONY]

THANK YOU guys i tried again by going on the rooftop again and still it places the HOMEPOINT at exact same location....

I took another picture of the MAP...Actually my building is around 400-500 Metters from that water place (where i put that piece of paper on Ning Street)

i'm uploading the text log file in some minutes

 

[KONY]

here is the latest flight record link
from the record 20 min ago

Phantom Log Viewer - PhantomHelp.com

 

[KONY]

also the magnetic field interference appeared on the last picture attached is because i took a photo of the screen of the smartphone once i was back in my appart 3 floors below , so no GPS were available anymore...while i was on the roof flying some magnetic interference warnings would show at the beginning but would be cleared upon take off...

 

[msinger]

Your flight log shows a different home point location:
https://www.phantomhelp.com/LogViewer/TILAQBTWOTF0P1ENAQ2F

 

[John Shaw]

THANK YOU guys i tried again by going on the rooftop again and still it places the HOMEPOINT at exact same location....

I took another picture of the MAP...Actually my building is around 400-500 Metters from that water place (where i put that piece of paper on Ning Street)

i'm uploading the text log file in some minutes

That is a very different location than the "southern district office" stated originally. I would agree that error distance is unusual.

 

[KONY]

msinger where do you see the home point location on the link you sent ? i see only white dots corresponding to some warnings

 

[KONY]

That is a very different location than the "southern district office" stated originally. I would agree that error distance is unusual.

yeah i was a bit above that southern district location but my residence was not visible on that picture...so i just pointed to that sign to show which side i was located at

 

[John Shaw]

I would suspect that some of the GPS signals may be reflected or refracted off the tall buildings which would result in a miscalculated position.

 

[msinger]

You can find the home point coordinates if you download the CSV file. The home point was marked at 22.24875568, 114.1546359.

 

[KONY]

You can find the home point coordinates if you download the CSV file. The home point was marked at 22.24875568, 114.1546359.

indeed , i typed those in GOOGLE MAP and it directs to my exact location...then why the "internal DJI GO APP MAP" shows something else...which one is used for the RTH ?

Also you told me earlier that switching ON the phone's GPS does not matter because the Aircraft uses its own GPS but i noticed this : whenever, after switching on the Remote controler once, i clicked on the map at the left bottom on the screen of my smartphone, it would pop up a message asking me to switch on the phone's GPS.

Only after that it will display the map on DJI GO APP.

Tha's weird then

 

[KONY]

I would suspect that some of the GPS signals may be reflected or refracted off the tall buildings which would result in a miscalculated position.

That could be true...but then, at same time, as Msinger pointed out, the GPS coordonates on the log file are correct : issue seems to come from the Internal MAP on the DJI GO app.

Firmware is not a cause because just before those flights i updated the latest firmware today. and DJI Go app is also the latest version available on android market.

 

[msinger]

after switching on the Remote controler once, i clicked on the map at the left bottom on the screen of my smartphone, it would pop up a message asking me to switch on the phone's GPS.

Only after that it will display the map on DJI GO APP.

What exactly did you switch on? It sounds like you turned the cellular data back on -- allowing the map image data to be downloaded and displayed.

 

[KONY]

actually data was already ON on the first flight (i had to switch data ON to update the battery), then that's when i decided to check my position on the MAP provided by the DJI GO app (that very picture i uploaded here)...so i clicked that small window on the bottom left corner of the DJI Go app..that's when the app prompted me to switch ON the GPS (that is the phone's GPS) because it needed that...indeed it's only after i toggled ON the phone's GPS that the internal map embeded inside DJI Go app, was displayed.

so it seems the DJI Go app needs to have the phone's GPS activated to display that internal MAP...But, in my case, info of the location of the MAVIC's HOME POINT was wrong on that very same MAP.

 

[superdave5050]

That's where the Mavic thinks you are. That looks to be about 120 meters on Google Earth. It's not that unusual to see that type of error before the GPS refines it's position. I would expect you might have to pause and reset home when it improves unless there is interference for the buildings.

So how do you pause and reset home ?
I had the same thing happen yesterday, I drove to a new location had rotors stopped but upon lift off I noticed it still had old location on map as home, 2 miles away. this was even after I recalibrated compass
I will admit I was not sure if I was doing calibration correctly but I did have "ready to go on" screen. I called it a day and gave up.