I do the compass calibration for the spark and P4 using the same location on my property in order to have a zero baseline so I can verify the compass reading and how much it deviates over time.

  

  

Flight with error:

  

https://youtu.be/zev0SOC2EZY

  

Re-flight after calibration, hunting for interference but cannot find any:

  

https://youtu.be/uGfhgM6pySQ

  

So far had this 3 times:

  

  

First time after 42 flights, second time after relocating to new launch site, the compass deviation found before calibration was 205, still in the green.
Third time after 103 flights, compass deviation found before calibration was 85, still in the green. (recalibrating is required to fly without errors so why is the app not asking me to calibrate?)
The P4 has no problems in those 3 locations so after each calibration, I went back to the same locations and had no longer compass errors (max 15 minutes had passed when re-flying in same locations), so this error I think has nothing to do with some interference in the environment I was flying in.
I have launched from these locations dozens of times afterwards without any issues. I will keep on flying and see what the trend is on the deviation and hopefully end up with a value that tells me it's time to calibrate the compass.

  

  

Flying the spark in ATTI is fun but during these three occasions the compass in my opinion was behaving correctly, the spark flies in a straight line and forward, backward, left and right corresponds perfectly to the sticks.

  

  

Note: The third time spark was about 350 meters away from me and experience was key bringing it back since I could only see a dot in the sky, don't know the attitude of the AC, easy, push the stick forward and if dot moves to the right gently yaw right and the AC will come towards me, if the dot moves to the left gently yaw left and the AC will come towards me (beginners don't need ATTI to practice this one).

You might be calibrating a bit too often, especially if it is always the same location more or less.

Wachtberger Posted at 2017-9-23 11:19
You might be calibrating a bit too often, especially if it is always the same location more or less.

My spark is only being calibrated after each compass error and only when there is a deviation from the calibration baseline. Spark has been calibrated twice so far and i am up to 227 flights

Hecate Posted at 2017-9-23 11:30
My spark is only being calibrated after each compass error and only when there is a deviation from the calibration baseline. Spark has been calibrated twice so far and i am up to 227 flights

But "compass error" displayed on the screen of your App does not indicate the need for calibration. It indicates external interference on the compass of the Spark.

The You tube links are in my post but just in case the error is Warning in flight, working  IMU encounters heading exception, Warning compass error exit P-GPS

Wachtberger Posted at 2017-9-23 11:34
But "compass error" displayed on the screen of your App does not indicate the need for calibration. It indicates external interference on the compass of the Spark.

There is no interference at that location, i have been flying drones there for 2 years. I moved 30 meters compass in the green and the same error. The only way i could fly there was to re-calibrate the compass.

Hecate Posted at 2017-9-23 11:40
There is no interference at that location, i have been flying drones there for 2 years. I moved 30 meters compass in the green and the same error. The only way i could fly there was to re-calibrate the compass.

I checked out that site with my RF Analyzer and measured the magnetic field, no interference found and no magnetic field disturbances found.

Hecate Posted at 2017-9-23 11:48
I checked out that site with my RF Analyzer and measured the magnetic field, no interference found and no magnetic field disturbances found.

Then I would strongly recommend that you open a case with DJI support and send them all the flight data. They should analyse what is going on there with your Spark and hopefully can provide the solution or replace if defective.

Good analisys. the feeling i do have with the comon compass error is that is not related to a specific interference of one place. I flow in place were i did get compass error without having the error...

ZukySpark Posted at 2017-9-23 12:24
Good analisys. the feeling i do have with the comon compass error is that is not related to a specific interference of one place. I flow in place were i did get compass error without having the error...

I agree, something odd is going on with these compass errors, in my case i always have my basic tools with me like the RF Explorer, a radio frequency multi band analyzer if there was any interference i would have know about it in advance. The RF Explorer is a great tool, to comply with Canadian regulations one must ensure no interference is present, only way to guaranty that is to measure it and its very useful to hunt down locations of any jammers.

Hecate Posted at 2017-9-23 12:47
I agree, something odd is going on with these compass errors, in my case i always have my basic tools with me like the RF Explorer, a radio frequency multi band analyzer if there was any interference i would have know about it in advance. The RF Explorer is a great tool, to comply with Canadian regulations one must ensure no interference is present, only way to guaranty that is to measure it and its very useful to hunt down locations of any jammers.

Please follow the advice in 8#, we can help you find out the problem. Thanks for support.

Great analysis, I also think the compass error is not due to interference but a hardware problem? Software problem?

What do you mean by compass DEVIATION? where can I see it?

Pirikitto Posted at 2017-9-25 02:06
Great analysis, I also think the compass error is not due to interference but a hardware problem? Software problem?

What do you mean by compass DEVIATION? where can I see it?

Hi, this is what I call compass deviation: i calibrate the sparks compass at the exact same location on my property, compass values after calibration at that location are between 0 and 12 in the app. After flying i check the same values in the app. So on one occasion i found a value of 205 (app start to show red around 520) so that means the spark finds an interference of 205 while I know it should be between 0 and 12 my baseline i found calibrating on the exact same location on my property. To me it means the compass of the spark is drifting as I accumulate flights. 205 out of 520 that is 40% less tolerance to interference if encountered.   
And when i do calibrate the spark on my property its back to the 0 to 12 value in the app.
Hope this explains it.

Pirikitto Posted at 2017-9-25 02:06
Great analysis, I also think the compass error is not due to interference but a hardware problem? Software problem?

What do you mean by compass DEVIATION? where can I see it?

You can see the compass values in the DJI go4 app, press the copter icon on the top, than all the way on the bottom press censors, than on the top middle press compass.

I did a compass calibration a few days ago. And today ( at anothe place) i did calibrate the compass of the iphone and turned on the spark and placed the spark in front of the iphone.  The diference between iphone and spark was 15 degrees. It is time to calibrate again?

ZukySpark Posted at 2017-9-25 04:08
I did a compass calibration a few days ago. And today ( at anothe place) i did calibrate the compass of the iphone and turned on the spark and placed the spark in front of the iphone.  The diference between iphone and spark was 15 degrees. It is time to calibrate again?

Most likely it's phone issue. Do not calibrate Spark.
BTW Spark RC itself produce strong magnetic influence to phone compass. Try to check with phone located at some distance from RC.

ZukySpark Posted at 2017-9-25 04:08
I did a compass calibration a few days ago. And today ( at anothe place) i did calibrate the compass of the iphone and turned on the spark and placed the spark in front of the iphone.  The diference between iphone and spark was 15 degrees. It is time to calibrate again?

Was reading a post where the DJI admin states that the app compass is not being used by the spark for flight.

My experience with this:
Noticed the app compass being off 80 degrees to the left, so i went out into the field and relocated and re started until they where a match. Hovering at 6 feet height i started to yaw to the right and after 15 turns is was back 80 degrees out. After the last app update the attitude between AC and app compass stayed bang on until yesterday, noticed it 60 degrees off to left on flight 146, i am now on flight 227 did not calibrate and no issues so far, I am using the map to fly the the spark home since the heading indicator on the app is unreliable.

Seams to be one of those random intermittent things and bet is a software related issue.

ZukySpark Posted at 2017-9-25 04:08
I did a compass calibration a few days ago. And today ( at anothe place) i did calibrate the compass of the iphone and turned on the spark and placed the spark in front of the iphone.  The diference between iphone and spark was 15 degrees. It is time to calibrate again?

Hi, in order to ensure the area for calibrating the spark has no magnetic interference one could use a free app like Teslameter and measure the magnetic field prior to spark compass calibration (you could measure the magnetic field when the app compass is reading wrong as well but think will not find anything) , need to hold the phone or tablet very close to the ground when measuring the magnetic field.

Hecate Posted at 2017-9-25 02:31
Hi, this is what I call compass deviation: i calibrate the sparks compass at the exact same location on my property, compass values after calibration at that location are between 0 and 12 in the app. After flying i check the same values in the app. So on one occasion i found a value of 205 (app start to show red around 520) so that means the spark finds an interference of 205 while I know it should be between 0 and 12 my baseline i found calibrating on the exact same location on my property. To me it means the compass of the spark is drifting as I accumulate flights. 205 out of 520 that is 40% less tolerance to interference if encountered.   
And when i do calibrate the spark on my property its back to the 0 to 12 value in the app.
Hope this explains it.

Thank you! I guess I understand, the value you're referring to is the 259 of the photo?

That value from me is very variable in the same place
You say it can be taken as a reference point to figure out if you calibrate the compass?

Pirikitto Posted at 2017-9-25 05:07
Thank you! I guess I understand, the value you're referring to is the 259 of the photo?

That value from me is very variable in the same place

Yep that is compass value, its very sensitive and will vary, after i calibrate mine it jumps between 1 and 12 and when i move the AC 10 inches to the left it jumps a little more.

Pirikitto Posted at 2017-9-25 05:07
Thank you! I guess I understand, the value you're referring to is the 259 of the photo?

That value from me is very variable in the same place

It is imported to calibrate at a location that has the least magnetic interference so it would allow the spark to handle the most EMF in the air.

Perfect!!
Thank you!!

fans04bc4ba7 Posted at 2017-9-25 04:31
Most likely it's phone issue. Do not calibrate Spark.
BTW Spark RC itself produce strong magnetic influence to phone compass. Try to check with phone located at some distance from RC.

Easy to tell if its a phone issue North indicator should be off as well...just my two cents.

Hecate Posted at 2017-9-25 06:08
Easy to tell if its a phone issue North indicator should be off as well...just my two cents.

I tried to run the program showing magnetometer value and found that my iPhone SE inserted to RC with home button to the right showing about 5 times greater (about 250 mT) than normal value. So I doubt if phone compass can show correct North under strong magnetic interference.

Hecate Posted at 2017-9-25 05:03
Hi, in order to ensure the area for calibrating the spark has no magnetic interference one could use a free app like Teslameter and measure the magnetic field prior to spark compass calibration (you could measure the magnetic field when the app compass is reading wrong as well but think will not find anything) , need to hold the phone or tablet very close to the ground when measuring the magnetic field.

Hello Hecate, I think your tips are very good for my problem and so yesterday I downloaded the app Teslameter. I get values between 43 and 51 (at home, in front of the house or in the field and so on).
Is this ok/can I start there or what I have to do?
Thanks!!!

gkrause Posted at 2017-11-19 07:09
Hello Hecate, I think your tips are very good for my problem and so yesterday I downloaded the app Teslameter. I get values between 43 and 51 (at home, in front of the house or in the field and so on).
Is this ok/can I start there or what I have to do?
Thanks!!!

Hi, find a spot with the lowest value outdoors and use it as your reference point even when the app shows a value around 43. The app measures the magnetic field of the planet so it will never be zero.

I have had my Spark for almost 2 month and I have flown a lot in different locations, some as far as almost 400 km away from my ussual flight location and I have never recalibrated my drone, and it has never acted in a strange way...