[REPORTED] TCN/WAYPOINT OFFSET function uses double variation?

[Bog9y]

Hi guys,

 

Just formally raising the bug of the offset function.  I haven't got screenshots or a trackfile because this bug is easy to check but if it's absolutely needed I can make those. 

 

So, to test the TCN offset function I am parked at Kobuleti with TRUE unboxed on the EHSD and do as follows:

 

1) Tune Senaki TCN 31X 

2) note BRG and DME to the TCN , for example 005 degrees at 20 nm

3) create OFFSET from TCN with BRG 185 and range of 20 nm

4) select T/OS steering and note radial and bearing to the offset waypoint. It should in theory be 0 nm but it will read something like 4 or 5 nm to the east. 

 

To fix this you have to apply DOUBLE the variation of the map. At Kobuleti the magnetic variation is 6ish degrees E. So in this example we have to add 2x6 = 12 degrees to the bearing in order to get the T/OS to be at the correct position.  When you do this with the example above and put in a bearing of 185+12 degrees = 197 you will get a T/OS that's 0.1 or up 0.3 nm away. This leads me to believe that the VARIATION has been applied in the wrong direction in the coding of this function.  If you use TRUE on the EHSD the variation has to be added only once to get the correct offset position. 

 

The same happens when you create a WAYPOINT OFFSET. Quickest way of testing this is by placing a waypoint exactly on the TCN station and performing the same steps as for the T/OS function test above. 

 

This also happens on the Syria map and Nevada but in Nevada the error is much bigger due to the bigger mag variation.  

 

The TAC-000 manual states: 

 

1.12.6.4.6 Waypoint Offset Entry. The waypoint offset range and bearing can be entered to the nearest hundredth of a nautical mile (0.01 nm) and tenth of a degree (0.1), respectively. The ability to enter waypoint offsets using a magnetic reference is available. The waypoint offset bearing entered is interpreted as a magnetic reference if the map menu (MAPM) TRUE option is not boxed. If the TRUE option is boxed the waypoint offset bearing will be interpreted as a true bearing reference from the waypoint. If the waypoint offset bearing is entered in magnetic reference and then TRUE is boxed, the waypoint offset bearing will update as local magnetic variation changes.

 

Edited June 26, 2021 by Bog9y

[Hornet81]

Hi @Bog9y,

 

Thanks for the detailed report. We will run some tests using your escenario and see if we can reproduce the same issue.

 

Regards

 

[Bog9y]

37 minutes ago, Hornet81 said:

Hi @Bog9y,

 

Thanks for the detailed report. We will run some tests using your escenario and see if we can reproduce the same issue.

 

Regards

 

Hi Hornet, many thanks for looking into it. Just bear in mind that I used the bearing and distance numbers just as an example, the exact numbers will ofcourse depend on where you are in relation to the TCN or waypoint. 

[Wisky]

from the other thread:

 

hm weird.

we used the f10 map to get a radial and range for suhkumi airport from the kobuleti tacan. and once i switched the ehsd to true and intercepted the r-303 outbound i arrived right on top of suhkumi.

 

if its off now then thats caused by the patch we got last week

 

--------------

 

i have just tried this on persian gulf

 

[Bog9y]

14 hours ago, Wisky said:

from the other thread:

 

hm weird.

we used the f10 map to get a radial and range for suhkumi airport from the kobuleti tacan. and once i switched the ehsd to true and intercepted the r-303 outbound i arrived right on top of suhkumi.

 

if its off now then thats caused by the patch we got last week

 

--------------

 

i have just tried this on persian gulf

 

Hey Wiskey, I'm not saying that the radial function is bugged. It's the offset waypoint that is bugged.  If you look at your screenshot from the PG, what I can see there is you have a TCN OFFSET set with a 353 bearing, and the T/OS waypoint is 2.6 nm from you. The TCN station is on a 179 bearing from you (you are on the TCN 359 radial). And if this is with TRUE selected you still have the "double the variation" issue. Do you see what I mean?   

 

For an easy test of this error i use my current position whilst parked up but you could also put a target on the 360 radial at 20 nm from a TCN. Then create the OFFSET from the TCN  (360 brg & 20 nm dist).  Fly to the offset and see where the target is, it will no be where you are, it will be at least 2+ nm away , possibly up to 4nm away, depending on variation and if you use TRUE or magnetic on the EHSD. 

 

This offset issue has been around for at least 6 months (since I started learning the Harrier) but I never formally raised the bug. 

 

[Wisky]

ok so this might have been a bit much without explaining anything.

my ehsd was not set to true

 

i simply created a tacan offset from al minhad afb to dubai intl. on the r-353 for 13.9 nm. 

 

and if you look now on my ehsd in the cockpit you will see that the tacan offset is rougly at where dubai intl. is located.

[Hornet81]

@Bog9y @Wisky

 

I have been running some tests regarding the TCN offset. The position of the TCN offset point in my tests were correct and quite accurate. In the example I wanted to add an offset point on the radial 090/2.5 NM from the KBL TCN. I added a HMMV on the sample place, radial 090º/2.499 miles from the KBL.

I have introduced the RADIAL 090º on the BRG box from ODU and 2.499 in the RANGE with T/OS boxed. The T/OS point goes in the correct position. 

Flying towards the offset point the plane overflies the T/OS with a precision of +/- 300-400 m error which it could be because of multiple errors like not placing the HMMV in the perfect place, flying error, etc. The error does not look too big for me however I will send that to Razbam and see what they think about that.

I tested with both TRUE and MAGNETIC with the same result.
 

Edited June 27, 2021 by Hornet81

[Wisky]

you wouldnt see a error on that distance really. you should try with something 60+ nm

 

i dont think the tacan offset is not working. But it should at least work with magnetic. (so you shouldnt just pump in the brg from the f10 map, but add the magnetic variation to it)

[Hornet81]

@Wisky @Bog9y

After more tests performed it seems to me that the issue is due to the wrong application of the Variation. 

The higher the variation (Nevada variation 12.1 E) the farther WEST the T/OS position is compared with were it should be. 

 

I add that to the bug system so they can fix that in the next update.

 

Thanks again for the reports.

Edited June 28, 2021 by Hornet81

[Bog9y]

11 hours ago, Wisky said:

you wouldnt see a error on that distance really. you should try with something 60+ nm

 

i dont think the tacan offset is not working. But it should at least work with magnetic. (so you shouldnt just pump in the brg from the f10 map, but add the magnetic variation to it)

That's the thing I haven't checked yet myself, the F10 map bearings...are they magnetic or true?  I guess true based on what you said here. 

9 hours ago, Hornet81 said:

@Wisky @Bog9y

After more tests performed it seems to me that the issue is due to the wrong application of the Variation. It seems that is codded in the wrong direction in all maps.

The higher the variation (Nevada variation 12.1 E) the farther WEST the T/OS position is compared with were it should be. 

 

I add that to the bug system so they can fix that in the next update.

 

Thanks again for the reports.

Cool, thanks Hornet. And like Wisky said, in order to see the error the distance needs to be greater.  Also, it may be worth checking the waypoint offset too and see whether that has the same error or if its just TCN. I'll see if I can do that test today. 

[Hornet81]

@Bog9y
The F10 Map is a grid north. 
I tested the Waypoint offset as well and you don’t get that error. It only happens with the T/OS. 

Edited June 28, 2021 by Hornet81

[Bog9y]

 

On 6/28/2021 at 9:38 AM, Hornet81 said:

@Bog9y
The F10 Map is a grid north. 
I tested the Waypoint offset as well and you don’t get that error. It only happens with the T/OS. 

 

Hi Hornet, I just tested the waypoint offset function and it does have the same error except it's only 1 time the variation error.  Because the F10 map uses True north the bearing is different than what you get in the HUD or EHSD.  To test this, go to mission editor , a/c hot start on ground, create 1 waypoint north of you by around 20 nm.  

 

In the mission, check the HUD to see what the bearing and distance is to waypoint 1, then create the offset with the reciprocal of that waypoint bearing. You will see that the waypoint offset point will be 2.3 nm or so away. If you then add the magnetic variation to the offset bearing you will see that the waypoint offset point will be 0.2-0.3 nm away which is more correct. 

[Hornet81]

@Bog9y,

 

Yes I noticed that it was just one time. I filled the report as the variation correction was not applied, and this happens in all maps. 
So they are working on it now to fix it and should be solved in the next update.

 

Thanks again for the report

[Kappa]

This bug is still a thing, right?

[Hornet81]

@Kappa

 

This has been resolved internally. Should be fixed in the next update. 
 

[Kappa]

2 ore fa, Hornet81 ha scritto:

@Kappa

 

This has been resolved internally. Should be fixed in the next update. 
 

Thank you