Author Topic: it seems there is some ILS/LOC/DME misalignment  (Read 22884 times)

G.Bosak

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it seems there is some ILS/LOC/DME misalignment
« on: March 11, 2013, 03:10:25 pm »
Hi Umberto,

ILS 26L "IFZ" should be placed 9,2DME from NOXOB

08L doesn't have the loc course 282 anymore it is 283° meanwhile.

I didn't have the time to check all runways yet, but i hope you'll have an eye on that. thank you

I wonder why so many developers don't wanna touch the fsx airport navaids to sync them with AIRAC data, i see it as elementary to have
proper navaids when buying any addon airport. It's a primary motive i purchase them, beside using up to date AIRAC data.

regards

virtuali

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Re: it seems there is some ILS/LOC/DME misalignment
« Reply #1 on: March 12, 2013, 01:16:15 am »
ILS 26L "IFZ" should be placed 9,2DME from NOXOB

That's exactly were it's placed, see the attached screenshot with the airplane placed at NOXOB, DME for 110.70 shows 9.2

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08L doesn't have the loc course 282 anymore it is 283° meanwhile.

That's the magnetic heading. ILS course are programmed in the scenery as true headings, and they never change (unless the ILS is really reconfigured) What you see in your instruments, instead, is magnetic, so it's affected by the magvar variation database is installed in your FSX.

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I didn't have the time to check all runways yet, but i hope you'll have an eye on that. thank you

We already have, before release, we went to each and every navaid of every approach, manually tuned the ILS and checked all the DME to be correct, and they were.

Check you don't have another AFCAD in conflict. What DME you read at the coordinates of my screenshot ?

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I wonder why so many developers don't wanna touch the fsx airport navaids to sync them with AIRAC data, i see it as elementary to have proper navaids when buying any addon airport. It's a primary motive i purchase them, beside using up to date AIRAC data.

Who said we HAVEN'T "touched" them ?

In fact, if you open the CYVR AFCAD with any AFCAD editor, you'll will notice that ALL ILS localizers and DME HAVE been changed by us (AFX, for example, will show them all as being "user modified"), for the precise reason the default ones have usually DMEs misplaced. They were corrected. If you don't read the correct DME, seems to indicate a conflict caused by another AFCAD somewhere.

What we are (and no wonder other developers share the same view) not too keen touching, is changing other items in the area, like terminal VORs, and there are of course sound reasons for this: the first one is that only a fraction of users updates their AIRAC data. Even less now there are not so easily (=free) available as they were before. It would be very wrong to *assume* everybody would always have the latest data.

Suppose something that affects multiple things (it has happened at places we were working on, Zurich at a certain date removed most of the VORs in the area and replaced it with GPS fixes, changing ALL their published approaches AND Sid/Stars AND even lo/hi routes), it would cause problems everywhere, especially for the approaches. Or simply confusing situations, such frequencies that were present in the default scenery that in real world would be assigned to different navaids.

We are of course forced to verify all approaches, when something is changing and is affecting the airport *design*, most obvious example is when new runways are added, such the case of O'Hare. In that case, we HAVE provided new approaches too.

The only solution that makes sense, is being sure the scenery is coherent with the charts SUPPLIED WITH IT, and that's it. This means the scenery will always be usable even years from now, without requiring to supply users with new charts AND scenery updates each time there's an AIRAC update that relates to the scenery. If we were trying to follow that route, the scenery would have to be sold as a subscription.

I'd say that, since there are developers who ARE in the business of charging for regular Navdata updates, same as they supply FMC databases for popular add-ons airplane, they could also supply .BGLs containing ONLY Navaids that, when put on an higher layer in the Scenery Library, could update any airport (default or 3rd party) to be compatible with they data THEY are selling.

This would suit both users: those that are happy with the default FSX scenery and whatever updates comes from a 3rd party add-on and DO NOT subscribe to those services, and those that DO subscribe, and want everything to be current. It will work WAY better if both the FMC navdata and the navigation BGLs would be supplied by the same people, from the same data source, rather then trying to convince each and every scenery developer out there to keep all their products constantly updated with AIRAC cycles.

G.Bosak

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Re: it seems there is some ILS/LOC/DME misalignment
« Reply #2 on: March 12, 2013, 11:32:35 am »
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That's exactly were it's placed, see the attached screenshot with the airplane placed at NOXOB, DME for 110.70 shows 9.2

thank you for you reply. I see no screenshot attached, but i haven taken one by myself and attached it.  :)

The radius is taken from FIX IFZ and should perfectly match NOXOB. NOXOB in Navigation display should be georeferenced because it is AIRAC data.

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That's the magnetic heading. ILS course are programmed in the scenery as true headings, and they never change (unless the ILS is really reconfigured) What you see in your instruments, instead, is magnetic, so it's affected by the magvar variation database is installed in your FSX.

Thats one thing i missed to renew after my actual installation, i'll check it. And you're sure, after replacing the magdec.bgl it will show me the correct magnetic heading of 283? I've always been thinking this update doesn't affect the airport Navaids?? I'll give it a try later.

i have to leave for the moment , but will reply on the rest later.

regards
« Last Edit: March 12, 2013, 11:34:52 am by G.Bosak »

virtuali

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Re: it seems there is some ILS/LOC/DME misalignment
« Reply #3 on: March 12, 2013, 12:28:10 pm »
Sorry, here's my screenshot which shows the DME is spot on at NOXOB. I've took the lat/lon coordinates for it from skyvector.com and manually positioned the airplane there.
« Last Edit: March 12, 2013, 12:31:01 pm by virtuali »

G.Bosak

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Re: it seems there is some ILS/LOC/DME misalignment
« Reply #4 on: March 12, 2013, 02:58:47 pm »
Sorry, here's my screenshot which shows the DME is spot on at NOXOB. I've took the lat/lon coordinates for it from skyvector.com and manually positioned the airplane there.

So then Skyvector is wrong, too  ;)

here you have actual real world data taken from jeppesen:

NOXOB
Airport:   CYVR
Latitude:   N49° 09.5'
Longitude:   W122° 56.1'
Flags:   Named Intersection, Final Approach Course Fix
Magnetic Variation:   17.0°E


which perfectly matches the PMDG AIRAC data from Navigraph/jeppesen:

NOXOB 49.158636-122.934392

I also wonder, why the GS of 26L catches as it should though the DME distance is demonstrably wrong.





virtuali

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Re: it seems there is some ILS/LOC/DME misalignment
« Reply #5 on: March 12, 2013, 04:20:49 pm »
So then Skyvector is wrong, too  ;)

Doesn't change much, see the updated screenshot exactly at the coordinate you reported, it's even possible that if we had that fix coordinates precise to the decimal second, instead of the decimal minutes, it might show 9.2 instead of 9.3, because it's just a bit on the threshold between the two.

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here you have actual real world data taken from jeppesen:

Doesn't change much, just 0.1 nm difference, which is not like what you show on your screenshot.

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I also wonder, why the GS of 26L catches as it should though the DME distance is demonstrably wrong.

The distance is correct within 0.1 NM, while your screenshot show a MUCH larger difference, so clearly the problem is not the scenery. You can verify this by simply LOOKING at the DME position in the scenery AFCAD with AFX or ADE, so you'll see it matches exactly the real world position, close to the start of the runway, a bit on the left side. In the scenery you can even see the antenna.

virtuali

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Re: it seems there is some ILS/LOC/DME misalignment
« Reply #6 on: March 12, 2013, 04:28:34 pm »
which perfectly matches the PMDG AIRAC data from Navigraph/jeppesen:

NOXOB 49.158636-122.934392

Exactly as I've thought, if I insert THESE coordinates in the FSX Map, it converts to slightly different lat/lon decimal minutes compared to the data from jeppesen in decimal minutes you posted (because of rounding issues), and the result is PERFECT, 9.2 NM and perfect alignment with the runway, as you can see from the attached screenshot.

Note the altitude and the Glidepath: as per published procedure, the glidepath intersects the NOXOB fix at 9.2 NM at 3000 ft: if this doesn't finally prove the utmost accuracy of the DME, I don't see what else does.
« Last Edit: March 12, 2013, 04:31:32 pm by virtuali »

G.Bosak

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Re: it seems there is some ILS/LOC/DME misalignment
« Reply #7 on: March 12, 2013, 05:47:04 pm »
I'm not spending further thoughts on 0,1nm rounding issues, that has never been a main problem, i'm asking myself how it comes to the ~2nm IFZ DME misalignment

I'm not fit with the editors you use, i can only check with my cockpit-instruments.

I've taken the ILS position data from AIRAC now, which should be again Jeppesen/Navigraph:

IFZ  ILS  49.190633-123.212544110.70T

Does it match your ILS scenery position? I am nearly running out of ideas now. If the aircraft uses its own data for every navaid the distance measuring would match again, because this is all
realworld referenced data. I've done the same with other airports like the new DubaiX and this test worked perfectly.

But if i have a look on your PFD, i wouldn't assume you are following a 3° GS, this is more likely a sarajevo approach.  ;)

Dave_YVR

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Re: it seems there is some ILS/LOC/DME misalignment
« Reply #8 on: March 12, 2013, 07:59:12 pm »
 I show the IFZ GP/DME site from the ADE file as 49.190623 -123.212562 which puts you right at the TDZ in the scenery. I also looked from within the PMDG NGX and was at NOXOB at 9.2DME. The actual DME and ND were pretty much spot on.

virtuali

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Re: it seems there is some ILS/LOC/DME misalignment
« Reply #9 on: March 12, 2013, 08:10:27 pm »
I'm not spending further thoughts on 0,1nm rounding issues, that has never been a main problem, i'm asking myself how it comes to the ~2nm IFZ DME misalignment

There isn't any misalignment, the rounding issue is not in the scenery, it's the difference between the coordinates you supplied in this format: N49° 09.5', W122° 56.1' (Jeppesen), which gives 9.3, compared to the same coordinates you supplied in THIS format: 49.158636-122.934392 (AIRAC), which gives 9.2 so, the rounding issue affected only my 1st screenshot, but the 2nd, one with the most precise coordinates you also supplied, was perfect.

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I'm not fit with the editors you use, i can only check with my cockpit-instruments.

You don't have to, just see my screenshot, it shows (check the coordinates) I AM in the real world NOXOB location, per your coordinates, and it shows 9.2 on the DME, tuned on 110.70, what ELSE you need to be convinced the scenery is correct ?

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I've taken the ILS position data from AIRAC now, which should be again Jeppesen/Navigraph:

IFZ  ILS  49.190633  -123.212544 110.70 T

Does it match your ILS scenery position?

Obviously not, because you are now confusing the Localizer position with the DME.

Your coordinates match 100% the scenery for the Localizer, which is on the far end of the runway. The DME, which is what we are discussing now, as I've said, it's on the near end of the runway, on left side.


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I am nearly running out of ideas now

As I've said, in might be either another scenery in conflict OR a problem with your instrument distance circle OR the navaid position for this specific fix.

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But if i have a look on your PFD, i wouldn't assume you are following a 3° GS, this is more likely a sarajevo approach.  ;)

I don't know what you are trying to say here: the ILS HAS a 3° GS, which is supposed to result in the Glide signal being intercepted at 3000 ft when 9.2 miles out. Since my screenshot clearly shows that I WAS 9.2 NM out and I WAS at 3000 ft and the GS in the scenery IS 3° (like most of all GS, and yes, I've obviously checked that too), it's fairly clear that I WAS on a 3° intercept path.
« Last Edit: March 12, 2013, 08:13:42 pm by virtuali »

G.Bosak

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Re: it seems there is some ILS/LOC/DME misalignment
« Reply #10 on: March 12, 2013, 08:19:12 pm »
I also looked from within the PMDG NGX and was at NOXOB at 9.2DME. The actual DME and ND were pretty much spot on.

Would you mind taking a screenshot of your situation in NGX.

I can't believe that i am alone with this effect:



« Last Edit: March 12, 2013, 08:29:26 pm by G.Bosak »

virtuali

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Re: it seems there is some ILS/LOC/DME misalignment
« Reply #11 on: March 12, 2013, 08:20:10 pm »
I show the IFZ GP/DME site from the ADE file as 49.190623 -123.212562

Nope. That would be Localizer coordinates, on the far end of the runway. the DME for this ILS is NOT co-located on the Localizer, it's located on the Glide transmitter!! Those are the coordinates: N49.183868, W123.165630.

This is exact how it is in real world AND on the scenery (we also put two visible antennas, one for the glide and one for the dme), with the AFCAD we supply. Please, check the charts at page 40 of the manual, it clearly shows the Glide being located on the *near* end of the runway, shown as a box, with its DME label.

In fact, the reported 2.0NM difference looks like like runway length, that would result if another (incorrect) AFCAD, with the DME located on the localizer would be in use instead of our AFCAD.

G.Bosak

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Re: it seems there is some ILS/LOC/DME misalignment
« Reply #12 on: March 12, 2013, 08:27:07 pm »
I show the IFZ GP/DME site from the ADE file as 49.190623 -123.212562

In fact, the reported 2.0NM difference looks like like runway length, that would result if another (incorrect) AFCAD, with the DME located on the localizer would be in use instead of our AFCAD.


i checked it meanwhile with airport scanner:

the afcad from ORBX Vancouver is deactivated ,nothing else installed. (screenshot attached)

Btw. did the magdec.bgl update meanwhile, still wrong LOC course 08L






virtuali

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Re: it seems there is some ILS/LOC/DME misalignment
« Reply #13 on: March 12, 2013, 08:35:22 pm »
i checked it meanwhile with airport scanner:

That means you have a conflicting scenery which the scanner couldn't detect.

Check another screen, this time with the PMDG, everything shows 9.2. I can't show the same screen you have, because I don't have the latest FMC database installed, so there's no NOXOB fix in my PMDG ND, but I AM at NOXOB, from the coordinates.

virtuali

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Re: it seems there is some ILS/LOC/DME misalignment
« Reply #14 on: March 12, 2013, 08:53:37 pm »
And if it wasn't enough, here's further proof from ADE: I've added the NOXOB waypoint at the exact coordinates you reported, traced a measuring tool up to the location of the DME in the scenery and, of course, the line reads 9.2NM in lenght.