[REPORTED] COURSE LINE abeam distance bug

[Bog9y]

There seems to be a bug with the course line abeam distance. 

 

It seems that the course line is based on TRUE heading not MAGNETIC in DCS, this is incorrect, it should be MAGNETIC.

 

When you set a course of say 360 degrees , fly abeam it at say 5 nm on heading 360 or 180 degrees with no wind, you will notice that distance will increase/decrease gradually, even though you are flying exactly on a parallel heading as the course.  I noticed that if you add the magnetic variation to the course line on the EHSD you fix this problem. So for this example, if it's the Caucasus map (with mag var of 6 deg W) ,you make the course 006 , fly 360 or 180 degrees and your abeam distance will not change.  In Nevada you have to add 13 degrees to fix this bug.   

 

Note, I only tested this with course lines from waypoints, not Tacans. 

 

Note 2: In the past the UFC used to display the true track, this got changed to magnetic a few months ago but I think the fix is incorrect and has instead turned the EHSD course to TRUE and not both to MAGNETIC. So I believe both the UFC and EHSD are now showing TRUE.

Edited September 9, 2021 by Bog9y

[Ramsay]

43 minutes ago, Bog9y said:

In Nevada you have to add 13 degrees to fix this bug (even though the mag var there is EAST not WEST like Caucasus?).   

 

Both Nevada (+12°E) and Caucasus (+6°E) have easterly magnetic variations, that is, in both regions a magnetic compass will point slightly West of true north and needs a +ve value added to it, to point to true north.

 

MagVar = True - Magnetic

 

i.e.

 

• Batumi RWY 13 MagVar = 126°T - 120°M = +6°E

 

• Nellis RWY 03R MagVar = 40°T - 28°M = +12°E

 

The sign of MagVar is often confused in DCS as we often convert from the F10 map (True) to the cockpit (Magnetic) by subtracting the (positive) MagVar i.e.

 

• Batumi RWY 13 Magnetic = True - MagVar = 126°T - (+6°E) = 126°T - 6° = 120°M

 

With regards to the EHSD bug, it'd be useful if you could include a track demonstrating the problem.

 

IIRC the DCS EHSD should display the course line correctly and heading/course in either Magnetic OR True depending on the chosen Mag/True mode.

 

However it's possible UFC input still takes user input only as a TRUE heading, regardless of the selected compass mode. 

 

Edited September 9, 2021 by Ramsay

[Bog9y]

4 minutes ago, Ramsay said:

 

Both Nevada (+12°E) and Caucasus (+6°E) have easterly magnetic variations, that is, in both regions a magnetic compass will point slightly West of true north and needs a +ve value added to it, to point to true north.

 

MagVar = True - Magnetic

 

i.e.

 

• Batumi RWY 13 MagVar = 126°T - 120°M = +6°E

 

• Nellis RWY 03R MagVar = 40°T - 28°M = +12°E

 

The sign of MagVar is often confused in DCS as we often convert from the F10 map (True) to the cockpit (Magnetic) by subtracting the (positive) MagVar i.e.

 

• Batumi RWY 13 Magnetic = True - MagVar = 126°T - (+6°E) = 126°T - 6° = 120°M

 

With regards to the EHSD bug, it'd be useful if you could include a track demonstrating the problem. 

 

Ah ok , my bad i assumed one of them was east, one of them was west, I'll amend my original post.  Still, it doesn't matter if it's east or west with this bug, the abeam distance on the course line will still be incorrect. I'll post a trackfile later today.  

[Bog9y]

Here is the track file. 

 

What you can see is that I have waypoint at a bearing of 067 at 84.7 nm.  

When you select a course of 067 the course line should be close to my current position but it isn't, it says my abeam distance is 10 nm (south of my position). When you change the course to 074 the abeam distance is 0.3 nm (which is pretty accurate with a waypoint that far away). I change it back to 067 and it's 10 nm again. 

 

So, what I think is going on here is that somehow magnetic variation needs to be added to the course line to get the correct abeam distance calculation to happen, this is not correct because the EHSD map is in magnetic. 

 

CRS LINE.trk2

[Ramsay]

On 9/11/2021 at 8:30 PM, Bog9y said:

Here is the track file.

 

Thanks, I confirm your report.

 

Tested DCS 2.7.5.10869

Edited September 14, 2021 by Ramsay

[AlphaJuliet]

Hey, thanks for the report, i'm adding it to our bug tracker.

[Bog9y]

Just to confirm, the abeam distance bug has not been fixed with the last patch. The abeam distance factor is actual double now from what it used to be. I suspect the coding line has added or subtracted the magnetic variation 2 times now. So if you want a course of 360 in Caucausus you have to add 12(ish) degrees to the course in order to get the correct abeam distance. 

[AlphaJuliet]

Hey,

We've seen this, it should be fixed for next update, give me a heads up if not. 

[RED]

The heads up that this is not fixed in the Nov18 update. Just found this in the jet and then found this report.