AP_ExternalAHRS: Fixed InertialLabs External AHRS driver

[VSheleverIL]

1. According to the Inertial Labs INS documentation, for conversion accelerometer output data, the value of g = 9.8106 m/s should be used. Using the GRAVITY_MSS constant will increase accelerometer errors.
   

   ardupilot/libraries/AP_ExternalAHRS/AP_ExternalAHRS_InertialLabs.cpp

   Line 270 in ae19d03

   ins_data.accel = u.accel_data_hr.tofloat().rfu_to_frd()*GRAVITY_MSS*1.0e-6;

2. The differential pressure in the Inertial Labs INS data format is represented in mbar. Therefore, for use in the ArduPilot algorithm, the value must be converted to Pa (Pascal).
   

   ardupilot/libraries/AP_ExternalAHRS/AP_ExternalAHRS_InertialLabs.cpp

   Line 381 in ae19d03

   airspeed_data.differential_pressure = u.differential_pressure*1.0e-4;

3. Using the offset_bearing() function to calculate northing and easting speeds is incorrect in this case, so a direct calculation has been added.
   

   ardupilot/libraries/AP_ExternalAHRS/AP_ExternalAHRS_InertialLabs.cpp

   Line 353 in ae19d03

   velxy.offset_bearing(u.gnss_vel_track.track_over_ground*0.01, u.gnss_vel_track.hor_speed*0.01);

4. Following the recommendations of Inertial Labs, the output data format (data set) has been expanded to include the following data:

   • Dilution of Precision (there is used in the algorithm);
   • GNSS Heading, GNSS Pitch, GNSS Angles position type, GNSS Heading timestamp (сurrently not implemented in the ArduPilot algorithm.).

   Additionally, logging of these data types has been added.

[rmackay9]

Removing these definitions doesn't look right. I suspect this change was unintentional.

[rmackay9]

nitpick: white space at the end.

[rmackay9]

Hi @VSheleverIL,

Thanks for this. Could you correct the commit title so that it starts with "AP_ExternalAHRS:"? If you look through our commit history you'll see we always prefix our commits with the subsystem to make it easier to see what is affected by the commit. This is especially important during backports. To be clear I meant the commit title, not the PR title.

Could you also fill in the PR description including testing that has been performed?

[VSheleverIL]

Hi @VSheleverIL,

Thanks for this. Could you correct the commit title so that it starts with "AP_ExternalAHRS:"? If you look through our commit history you'll see we always prefix our commits with the subsystem to make it easier to see what is affected by the commit. This is especially important during backports. To be clear I meant the commit title, not the PR title.

Could you also fill in the PR description including testing that has been performed?

Hi @rmackay9,

Thank you for your feedback. I have made changes according to your comments. Please review the outcome. Thank you!