GPS Groundspeed Update Frequency 6030

[Kent]

Hi Pete,

Quick question. I have been comparing the outputs of the following two offsets. My application processes FSUIPC data at 10Hz. 0x2b4 seems realtime (expected), and the GPS version 0x6030 seems updated every 1 second. Is the GPS update frequency coming from the virtual GPS installed to the current plane, a generic fixed amount assigned to all aircraft from P3d/FSX, or is it an update limit placed on the value from FSUIPC? (Also note: I am using WideClient for this test).

 

private Offset<int> offGroundSpeed = new Offset<int>(0x2b4); // GS: Ground Speed, as 65536*metres/sec. Not updated in Slew mode!

private Offset<double> offGpsGroundspeed = new Offset<double>(0x6030); // GPS: aircraft ground speed, floating point double, metres per second.

 

Thanks!

Kent

[Pete Dowson]

16 minutes ago, Kent said:

Quick question. I have been comparing the outputs of the following two offsets. My application processes FSUIPC data at 10Hz. 0x2b4 seems realtime (expected), and the GPS version 0x6030 seems updated every 1 second. Is the GPS update frequency coming from the virtual GPS installed to the current plane, a generic fixed amount assigned to all aircraft from P3d/FSX, or is it an update limit placed on the value from FSUIPC?

It'll probably be the way the GPS in the aircraft works.   FSUIPC asks for updated values to be sent whenever the value changes by 0.1 m/s or more. It isn't time related. 0x2B4 is updated when it changes by 0.01 m/s or more, so they'll obviously be more updates for that.

Why would you want to use the GPS offsets in preference to the direct readouts from the simulation?

Pete

 

[Kent]

I'm writing an interface to Garmin Pilot, the 3rd party apps out there didn't work well for me. All the positional data works fine, working on traffic and AHRS now, if GP supports it (still unsure if it even does... need someone with X-Plane to tell me if it does).

 

I started looking at the GPS offsets to calculate the true groundtrack to feed to GP. After that I started taking a look at all of the other GPS offsets and comparing them to the non-GPS offsets for the same purpose. I started to consider if I should use all of the GPS offsets to Garmin Pilot so it more closely replicates GPS on the virtual aircraft. I decided my iPad updates at 10Hz IRL rather than 1Hz (with bluetooth GPS), so decided to send data to Garmin Pilot at 10Hz... but may change my mind again if this is plane-specific.

 

(C# ground speed)

this.groundspeed = Math.Round((((double)this.offGroundSpeed.Value) / 65536.0), 3); // 0x2b4 preferred
var gs = Math.Round(this.offGpsGroundspeed.Value, 3); // 0x6030 only updates once/sec in tests.. not used

 

(C# ground track)

var variation = radiansToDegrees(offGpsMagneticVariation.Value);
var magTrack= Math.Round(radiansToDegrees(offGpsMagneticTrack.Value),4);
this.track = Math.Round(radiansToDegrees(offGpsMagneticTrack.Value) + variation, 4);

 

I'll try giving a couple other planes a test and see what happens.

Thanks!