magn. north

[jd winchester]

Is it possible to set / check compass by: setting GPS (setup) to "magnetic north". Then relate the readout to how the compass reads?? (in calm air of course & no cross wind)
GPS should allow for deviation in the area your in,,, right?

Wouldn't this work if there were no compass rose available?

 

[Areeda]

I have verified the compass deviation card on the ground with a compass rose and GPS. If I taxied straight for not very far maybe 10 feet the ground track on the GPS lined up well with the compass rose, better than the magnetic compass.

I'm not sure I'd adjust the compass that way, but I gained a lot of confidence that the misalignment between the mag compass and the HSI was the mag compass.

Joe

 

[Henning]

Is it possible to set / check compass by: setting GPS (setup) to "magnetic north". Then relate the readout to how the compass reads?? (in calm air of course & no cross wind)
GPS should allow for deviation in the area your in,,, right?

Wouldn't this work if there were no compass rose available?

The GPS database will take into account local Variation. Deviation is the error in the compass installation. "People vary place by place, but there are deviants everywhere." is the memory aid I teach to keep that straight. As for correcting it's "True Virgins Make Dull Company Add Whiskey." You can check your compass off the COG of the GPS when set to magnetic, but you have t be danged sure you have no crosswind.

 

[poadeleted20]

It's theoretically possible, but the FAA doesn't authorize it for "official" compass swings. The technical problem is that GPS TRK isn't accurate unless you're moving, and if you're moving on the ground, it's hard to hold the track that precisely long enough to adjust the compass. In the air, the GPS TRK is useless for checking the compass since the wind is carrying you around and your heading and track are not the same. While in theory one could do that by flying exactly into or with the wind, or on a totally calm day, the wind is too variable to make it work accurately enough for a compass swing or to create a compass deviation card.