Version Information
26.1 (15475)
Device Information
iPad Air M3, iPad OS 26.2.1
Description
This is basically the issue reported in Bug report VOR directions. Bearings to NAV1 and NAV2 are indeed now fixed showing the same bearings, but the bearing to the station selected in SRC (in this case NAV1) is still showing offset.
@Jugliar, you mentioned that this is already fixed in one of the previous Beta versions (What is bearing 1 and/or 2 used for? - #3 by polaris-14). Can you confirm if it was indeed fix or if the behavior was the same as I described above?
That is normal. Bearing 1 and Bearing 2 from NAV1 and NAV2 are the same now, when tuned into the same VOR.
But:
ADF/ SRC (Source) shows a geometric bearing
NAV/ BRG shows a VOR radial/instrument bearing
Those are two different reference systems.
The bearings come from VOR navigation:
A VOR works with radials, not direct bearing and a radial is direction from the station outward
And here’s the important part: VOR indications are magnetically rounded and instrument-quantized.
They are not millimeter-precise GPS values.
So:
• SRC = exact mathematical bearing
• BRG = VOR system + OBS + instrument representation
→ small deviation is normal
(Edit: ADF added)
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And also: A VOR is referenced to magnetic north at the time it was originally calibrated. When the station is installed, it’s aligned with the magnetic north that existed at that moment, and that reference is basically “frozen in.”
The VOR doesn’t continuously update itself as Earth’s magnetic field slowly shifts over the years. Because the magnetic field drifts gradually, after some time you can end up with small differences.
For example, a chart or GPS calculation might show a magnetic bearing of 308°, while the VOR is effectively transmitting something like 306°. That’s simply because the VOR is based on an older magnetic reference. This is completely normal and well understood in real aviation, and VOR systems are built with tolerances that allow a few degrees of deviation.
And the ADF/ SRC system is based on GPS localization, which uses the momentary magnetic north, that’s also why deviations can occur.
I am sorry, I am not a native English speaker, so I hope it makes sense the way I wrote it.
(Edit: ADF added)
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And last but not least: See the green doted line in my mini map? That is the radial shown, when I turn the OBS to the 306 degree radial. Although the line does not completely go through my position, that’s the closest, I can get. One degree more or less is even more offset. So the VOR Bearing is always a bit different from the “Source” Bearing.
I am really horrible in explaining 
Sorry for that.
You’re not, actually… that was a very clear and concise explanation of the differences in behavior, and covers exactly why the GPS SRC bearing will differ in most cases.
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I think you are mixing the concepts of bearing, radial, and magnetic deviation a little bit, but I digress.
The bottom line of my bug report is that SRC shows true bearing while NAV1 and NAV2 show magnetic bearing. I am not sure why you would display one true and the others magnetic next to each other in this way.
I also don’t think SRC = GPS. In my interpretation, putting NAV1 or GPS in the SRC indicates the navigation source that I will couple with my autopilot (thus LNAV vs NAV1 tracking on the lateral navigation mode).
But if the developers have a software requirement different than my interpretation, you can close this working as designed.
I am sorry, when I misunderstood you. Nevertheless I am unable to find this following written statement in your bug report…
…rather than:
And in the mentioned thread I had only confirmed, that BRG1 and BRG2 are now showing same values, when tuned to the same station.
And in the end I have only given some reasons, why it is normal that VOR NAV Bearing can deviate from ADF/ SRC. And this is only based on my understanding. I can be wrong.
Nevertheless I am unable to tell where the deviation in IF derives from. I am unable to tell whether ADF/ SRC is showing true north or just a magnetic north deviation due to the above mentioned reasons.
I think for this, you need to ask the developers. But when I know also irl they can deviate, it is not a problem for me, since I am able to navigate successfully. And- I also might be wrong here and please if someone knows it better, please tell me- from what I understood, SRC / ADF would be rather used with an NDB for the exact mentioned reasons.
(Edit: ADF added)
But sometimes I really wonder, how many people here would still be able to navigate, if GPS and Autopilot would not exist.
In the 80’s when I was doing my first MSF II experiences on my Commodore 64 (), I had charts with the NDB’s and VOR’s and GPS didn’t even exist in the real world. And the Cessna (I believe) was the only plane to fly.
So I had to learn how to navigate by tuning into different VOR stations, set the right radial or making cross bearings with two VOR’s to determine my position on a map.
That was very helpful.
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