NZAA Offset Centerline - Issue is back

[cstigberg]

Evening,
Back in March of 2023 I brought up a topic about the centerline in Auckland. It was determined by Richard that the ILS antenna coordinates were not correct and a revision was made which resolved the issue. It’s been at least a year since I’ve flown into Auckland and now with the PMDG 777 out, I wanted to do a flight. Coming into 23L this evening, I discovered this old problem was back. I assume it was left out in an update at some point? Hoping we can get this fixed again. Thanks!

Please reference this thread here: NZAA offset centerline

[NAVDataOld]

Hi,
Welcome back … thanks for your report.

It´s clear, that this issue is “back”. As I have written in the reference posting, the root course of this issue is the wrong ILS antenna, which New Zealand offers the data provider. So, this is more an AIP issue rather an issue on our side.

But, as I have also written in the reference link, I have found a solution to “move” the ILS antennas more in the center line depending on the MSFS runways and that’s exactly also the answer of your “issue is back” now.

The solution works only in MSFS because I compare the runway-center lines from the MSFS with the real-world ILS antennas and “move” it center lined. The addon datasets can only used the real-world source data, that means that the PMDG uses the wrong AIP New Zealand antenna position and therefore the “issue is back”. So it´s not really back, the “fix” is only for the MSFS inside data but not for any 3rd party addon datasets.

We try to avoid to change the source data (due legal reasons and our contracts with Jeppesen). We trust the data and exactly in this situation, you see that this is an issue outside of the provider. I will look deeper on this after our summer break. Our data will be used in nearly all our apps so we must be careful when we make such “general” changes.

So, conclusion for now:
This is an issue in the AIP New Zealand, which can´t be fixed by us (nor by the data provider). This wrong antenna position must be changed by New Zealand to get a generic solution. We will look on solutions in the future - I will add it in our internal backlog system.

Cheers
Richard

[jpschuchna]

Hi Richard,

777 as well still uses the MSFS bgl databases for the ILS. Otherwise it wouldn`t be able to tune custom ILS that have nothing to do with real world:

EDDS RWY 25 as example with corrected Glide Slope elevation due to scenery design (flat RWY)

 <?xml version='1.0' encoding='ASCII'?>
<FSData version="9.0">
  <Airport lat="48.6898777261376" lon="9.22196388244629" alt="1255F" ident="EDDS" onlyAddIfReplace="TRUE">
   <Ils
                lat="48.684952304"
                lon="9.196054016"
                alt="373.075M"
                heading="251.0"
                frequency="109.750"
                range="27.0N"
                magvar="-2.987"
                ident="IABC"
                width="5.19999980926514"
                name="ILS/DME 25"
                backCourse="FALSE">
                <GlideSlope
                    lat="48.692385287"
                    lon="9.240224948"
                    alt="1259F"
                    pitch="3"
                    range="27.0N"/>
                <Dme
                    lat="48.692385287"
                    lon="9.240224948"
                    alt="1259F"
                    range="27.0N"/>
            </Ils>
</Airport>
   </FSData>

[NAVDataOld]

Two different pair of shoes. The PMDG uses NOT! the bgls from MSFS … but without the BGLs you can’t use the sim.

In this case, we don’t speak from elevation, frequency, … we are speaking from the position of the ILS antenna. Here, you have two values now, one real world value which is wrong according the AIP and one corrected value in the scenery.

I think, we should remove the aligment fix in MSFS BGLs to be in sync with all other addons too. I have explained in the reference link, that this is wrong alignment comes from the AIP New Zealand therefore it’s not a navdata issue … The root issue is the AIP.

I will look, if I remove the alignment workaround in the MSFS bgls.

Cheers
Richard

[hervesors]

@NAVDataOld

I have explained in the reference link, that this is wrong alignment comes from the AIP New Zealand therefore it’s not a navdata issue … The root issue is the AIP

Hi Richard,

I’m unsure the problem is the AIP
Looking at published LOC data for NZAA ILS 23L (IMG), reported coordinates in the AIP
[GEN_3.7.section]
are S37 01 04.20 - E174 45 54.90 (-37.0178333 174.7652500 in decimal format)
making loc antenna perfectly aligned with runway 23L whose coordinates are published in another section (4 ft offset)
[AERODROMES-AD1]
From data I have, it seems Jeppesen data are a bit different for this loc antenna
-37.0177944 174.7649361 resulting in a 50 ft offset
You may have a look to this

Regards

Hervé

[NAVDataOld]

Hi Herve,
possible, but can you confirm that the runway in the stock scenery is also correct according the AIP?

Also in the reference posting, the google map image looks not really aligned …

Cheers
Richard

[hervesors]

Hi Richard,

@NAVDataOld

can you confirm that the runway in the stock scenery is also correct according the AIP?

I cannot answer that since I do not own MSFS. It is not correct in P3DV5

Regarding AIP runway threshold coordinates, it appears they are correct and fit Google Earth data as well as Jepp data
-37.016317 / 174.770783 for Rwy 5R
-37.006656 / 174.805742 for Rwy 23L

Cheers
Hervé

[NAVDataOld]

Hi,
I have now cross-checked all - the position was changed in the current AIP:

Here the antenna coordinates from the ILS05 (IAA) from the current AIP:

Here, what Jeppesen offers:
S37002154 / E174482932

So, you see Jeppesen (our source) uses exactly the same coordinates as the AIP offers. Also these coordinates are correct now and center lined. So, that´s the initial position. The Jeppesen data are correct so far now.

I have also compared now the data from MSFS and here we have a offset now and the reason are the runway thresholds in the MSFS scenery. With the workaround, I aligned the ILS antenna position with the center line. That works because I have used the runway-coordinates from the MSFS which are not always 100% aligned with the real-world data. Due this delta now, you see an offset.

Solution for the future:
I will remove the workaround with AIRAC 2408 to avoid such deltas. In this case (NZAA) the ILS should be center lined again (also with the PMDG). With 2408 I will only use the real-world data and will not aligned it again with the center lines from the MSFS runways.

Cheers,
Richard