Haversine Forums -> AirTrack - General Issues and Support

HDG option

Posted on April 23, 2015 07:35 by pyrolex

Hi to all,

I think I have a little problem with the HDG setting running Airtrack with "Device Location Services" activated.
I recognized a different behaviour in the app running on my iPad compared to that on my iPhone.
Setting this option to COMPASS the compass in the PFD on my iPhone seems to run correctly but on my iPad it looks as if I set HDG to COURSE.

Can anyone confirm this?

Thanks and kind regards,

Posted on April 23, 2015 09:06 by haversine


This should depend on the iPad model you have. If you iPad has an internal compass/ magnetometer, it should use it for HDG. Otherwise HDG will be derived from COURSE. I believe iPad1s didn't have a compass but can double-check. Which model do you have?

Same applies for the gyro, devices without a gyro (such as the iPad1) will not have yaw and will derive roll and pitch from the accelerometers, whereas those with gyro will use it.

joao @ haversine

Posted on April 23, 2015 09:58 by pyrolex

Thanks for this quick answer.
I have an iPad mini retina with 3G/WiFi running iOS 8.3

The curious thing is, that when setting HDG to COURSE, the PDF seems to run in COMPASS mode and vice versa.
On my iPhone 5 running the same iOS version everything looks correct.


Posted on April 23, 2015 10:01 by haversine

Hi again,

Hum then it must be a bug ... Standby, I'll check on my iPad mini and come back.

thanks for spotting it,

Posted on April 24, 2015 20:34 by haversine

Hi again,

Just tested again on an iPad mini retina with WiFi only and it works as expected. I then tried with an iPad1 and it works too, so actually I was wrong, the iPad1 does have a compass, it is only older iPhone devices that don't have one.

So in summary, if you select HDG as COMPASS the device will react to heading changes. If you select HDG as COURSE the device will not, and will only update the heading when new GPS course data is received (every second or 2 if you're moving).

You can see this in the:

PFD only mode on the compass below the attitude indicator, moves when you rotate the device in compass mode
MFD or CFD mode, see the map moving when you rotate the device in compass mode

This however is not to be confused with MAP versus APP or VOR MFD modes; if you have your MFD set to MAP mode (the default) the top corresponds to COURSE or TRACK and you'll see TRK

If you select APP or VOR modes, the top will be compass driven and it will say HDG

If you select HDG as COURSE in settings then they'll both be the same; otherwise not.

This is how the Boeing 737's MFD works; you can toggle between does by tapping on the appropriate key.

hope this helps,

if not could you let me know exactly the steps you've taken,
could be that your iPad works differently somehow,
joao @ haversine

Posted on April 26, 2015 07:39 by pyrolex

You are absolutely correct!
I have found the reason for the behaviour described above:
I forgot to activate "Compass calibration" in the location service settings of iOS.
Now, everything works correctly.
Thanks for the trouble and sorry.
Keep up the good work! :)


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