How to get true track

[frazer84]

Is there any way to, via FSUIPC, get the aircrafts true track?

I've found the GPS-variable for track, but the update frequency is very bad, so it's unusable for user presentation stuff at least.

Is there any good and accurate way to calculate this using FSUIPC-offsets?

I've tried using the known mathematics to calculate the WCA (Wind Correction Angle) by using wind speed, wind angle, aircraft heading and aircraft airspeed (http://www.delphiforfun.org/programs/math_topics/WindTriangle.htm) but that doesn't give me accurate figures compared to the GPS track number.

Any ideas? Many addons have the track shown on the navigation display (for example all 737NGs with TRACK UP mode on the navigation display), so there must be a good way of doing it?

Thanks!

Regards,

Daniel

[Pete Dowson]

Is there any way to, via FSUIPC, get the aircrafts true track?

I've found the GPS-variable for track, but the update frequency is very bad, so it's unusable for user presentation stuff at least.

Real GPS updates aren't all that frequent in any case, and I would assume track takes time to compute because it involves taking two Lat/Lons and deriving the track from that. However, FSUIPC is simply getting the "GPS GROUND MAGNETIC TRACK" variable from SimConnect whenever it changes.

What sort of user presentation needs a faster update of track?

I've tried using the known mathematics to calculate the WCA (Wind Correction Angle) by using wind speed, wind angle, aircraft heading and aircraft airspeed (http://www.delphifor...indTriangle.htm) but that doesn't give me accurate figures compared to the GPS track number.

That's because a GPS track is based on a change of poistion. Any other method is really a guess.

Any ideas? Many addons have the track shown on the navigation display (for example all 737NGs with TRACK UP mode on the navigation display), so there must be a good way of doing it?

The track up on NDs is from the previous period, but presumably they simulate the IRS postion changes not the GPS.

How are you determining that your method is not as accurate as those in the add-ons you refer to? The GPS will usualy be more accurate in any case I think, because it is based on further distance travelled between Lat/Lon positions. The faster you want it, the less accurate, i would have thought.

Regards

Pete

[frazer84]

First, thanks for the quick answer.

Real GPS updates aren't all that frequent in any case, and I would assume track takes time to compute because it involves taking two Lat/Lons and deriving the track from that. However, FSUIPC is simply getting the "GPS GROUND MAGNETIC TRACK" variable from SimConnect whenever it changes.

What sort of user presentation needs a faster update of track?

Okey, I'm really simulating an IRS, not a GPS, which makes me want to have faster updates since an IRS has that.

The user presentation is a HUD, connected to a gyro platform (IRS), which doesn't look very good with the GPS update rate.

How are you determining that your method is not as accurate as those in the add-ons you refer to? The GPS will usualy be more accurate in any case I think, because it is based on further distance travelled between Lat/Lon positions. The faster you want it, the less accurate, i would have thought.

Well the track figure that I get vary very much compared to the addons I've tried, that simulate an IRS, which I guess has to do with airspeed being one of the input parameters in the calculation?

[frazer84]

A last update on this. I've succeeded with getting the true track by using the posted formulas out on the internet, but remembering to convert ALL angles to radians in the calculation.