X-Plane NAVAID inconsistency

[FltsimFlyboy 0]

Hi,

Can anyone please explain to me how X-Plane's navaids work with the navaid data? I am confused about the relation between the X-Plane's data, external data (Navigraph), X-Plane's art objects and the actual location of the navaid inside the sim.

I am specifically concerned about ILSs and VORs. While editing some airports using WED, I found some ILS localizers that are not placed at the correct location (completely shifted from the runway centerline). I know that shifted localizers exist, but that is not the case here. I validated the coordinates of the localizer antenna from official publications and satellite imagery. Mind you, this is not a small shift - the localizer source is 50m (165ft) left of the correct location, which causes a plane to land on the runway shoulder rather than the centerline.

I did some digging and found the default data that x-plane uses (resources/default data/earth_nav.dat) and checked the coordinates of the localizer. Weirdly, the coordinates don't match the one being shown in WED. They are (almost) aligned to the centerline, but the data is old (AIRAC 1708). In the data, the ILS is shown to be CAT-I, whereas, in reality it is a CAT-IIIB.

I updated to the latest AIRAC from Navigraph (in Custom Data/ and Custom Data/GNS430), thinking that it would fix the misplaced localizer. I verified the updated data, and it has the correct localizer coordinates! Also, the ILS there is mentioned correctly as CAT-III! I loaded the sim and tried to do an ILS approach. To my surprise, the plane landed at the same spot as before - on the runway shoulder.

I checked the following:

1. The correct (and current) AIRAC data is being recognized by the aircraft FMC/GPS - this means it is picking up the Navigraph data.
2. X-Plane's map still shows the ILS as CAT-I - this means the map is reading X-Plane's default data and ignoring the Navigraph data.
3. The actual art object for the localizer antenna in the scenery is at the incorrect location.
   • This location is where the source of the localizer in the sim seems to be.
   • This is the location that WED says the localizer is at.
   • This is the localizer that the aircraft is locking on to, regardless of updated navdata.

This image explains what I am talking about: https://1drv.ms/u/s!Ar2bPVs2rkEyqdYuYdeF7Y9AjmdP8w?e=mbSbAq

So, does this mean that the localizers/VORs are 'baked in' in the sim and cannot be updated? What is the benefit of getting updated navdata? Only the latest FIXes/Airways/Procedures (since these are the only things that are 'virtual' and do not have a physical presence inside the sim)?

I would really appreciate if someone can shed some light on to this navaid behavior.

Cheers,
Asmit

 

[JRBarrett 3,034]

The locations of ILS components for default XP airports are located in the following file:

X-Plane 11/Custom Scenery/Global Airports/Earth nav data/earth_nav.dat

This file contains what is known as “curated” data. It is provided only by Laminar and updated only when XP is updated. This file is linked to all the default airports in the X-Plane scenery gateway. https://gateway.x-plane.com 

This file takes priority over any other nav data files when it comes to airport ILS placement.

Navigraph does not currently update this file, because any errors here could possibly corrupt the ILSs for every default airport in the sim.

The monthly updates from Navigraph do update the in-sim geographic placement and frequencies of VORs, NDBs and any DMEs which are not part of an ILS, but the geographic placement, frequencies and courses of ILS localizers, glide slopes and marker beacons come only from the curated file.

The only way to override the curated ILS file is to install a custom airport replacement for a default airport - either one created by a scenery developer, or one you have created yourself with WED. The ILS data in the custom version of an airport will take priority over the curated ILS file.

The monthly Navigraph updates do provide current data for aircraft FMS systems, which is why your FMS correctly shows that the VECC ILS 01R is now a cat III but the updates do not change the ILS data in the default airport scenery.

However, this is apparently going to be changing in the near future. The current XP NAV data is in a format known as “XP1100”.

At least in the case of ILS data, it appears the format will soon be changing to “XP1150”, and the data for ILS systems in the sim airports scenery will be included in monthly Navigraph updates. This will require that you be running XP 11.50b1 or later. I found the following note on the XP Developer Blog:

“Curated localizer data is being deprecated, pending rollout of XPNAV1150 data. For Beta users who do not use Navigraph updates, the default navdata of X-Plane will be providing localizers exclusively. We expect to switch users of Navigraph updated data to the new localizer model as well soon. This section will be updated as new data becomes available for Beta users.”

“Everything you ever wanted to know” about XP nav data can be found here:

https://developer.x-plane.com/article/navdata-in-x-plane-11/

 

[FltsimFlyboy 0]

Thanks for clarifying. I also saw the post about XPNAV1150. I am running 11.50b4, but that version still has XP1100 format. I am guessing closer to the release they will transition to the XP1150 format, as will Navigraph.

However, there are two things that I still do not get:

Quote

The locations of ILS components for default XP airports are located in the following file:

X-Plane 11/Custom Scenery/Global Airports/Earth nav data/earth_nav.dat

 

As I mentioned in the post - for VECC 01R ILS, the actual ILS in the sim is not at the same location as specified in the default earth_nav.dat file. It seems to me that X-Plane has an embedded navaid database that you use in the sim. The default navdata is just doing what Navigraph does - provide fixes, airways, etc.

11 minutes ago, JRBarrett said:

The only way to override the curated ILS file is to install a custom airport replacement for a default airport - either one created by a scenery developer, or one you have created yourself with WED. The ILS data in the custom version of an airport will take priority over the curated ILS file.

I am creating a custom scenery of VECC with WED, but WED does not support editing/adding navaid data. It only shows the navaids that are present in the sim.

Anyway, thanks for the help! I guess I'll have to wait till the release of XPNAV1150 to see the corrected localizers.

[JRBarrett 3,034]

42 minutes ago, FltsimFlyboy said:

Thanks for clarifying. I also saw the post about XPNAV1150. I am running 11.50b4, but that version still has XP1100 format. I am guessing closer to the release they will transition to the XP1150 format, as will Navigraph.

However, there are two things that I still do not get:

As I mentioned in the post - for VECC 01R ILS, the actual ILS in the sim is not at the same location as specified in the default earth_nav.dat file. It seems to me that X-Plane has an embedded navaid database that you use in the sim. The default navdata is just doing what Navigraph does - provide fixes, airways, etc.

XP has so many files in different locations with the same name, it’s easy to pick the wrong one

I believe you are looking at:

resources/default data/earth_nav.dat

That file will control what you will see regarding ILS approaches in an XP FMS or GPS if you do not use Navigraph, BUT it does not actually place the ILS in the scenery. It does place VORs, and NDBs but not ILSs.

If you have Navigraph, the above file will be overridden by /custom data/earth_nav.dat, but again, although this file will place VORs or NDBs in the scenery, when it comes to ILSs, it only controls what you see in a GPS or FMS.

The file that actually puts ILS localizers in the scenery is located at:

Custom Scenery/Global Airports/Earth nav data/earth_nav.dat

If you look in the folder /Custom Scenery/Global Airports/Earth nav data/ with Windows Explorer, you’ll see dozens and dozens of sub folders with LAT/LON coordinates like “+40-76. The earth_nav.dat file is at the very bottom of the folder listing - you have to scroll all the way down to see it.

It’s yet another “earth_nav.dat”, file, but this particular one contains only ILS information, and the actual ILS placement in the scenery (including the visual representation of the ILS localizer antenna), come from this file, and only this file. The localizers are not baked into the scenery the way they are in FSX or P3D

Although this is a simple text file that you can open in Wordpad or Notepad, the XP Developer web site strongly cautions against trying to edit it. The only way to get this file corrected in the case of a mis-placed ILS, would be to post a note at the X-Place Scenery Gateway web site for the airport in question. But with the upcoming change to the XPNAV1150 file format and Navigraph involvement, it appears that the curated file will no longer be needed.

 

 

Edited April 28, 2020 by JRBarrett

[FltsimFlyboy 0]

Ahhh... my bad! I did not realize that there was yet another earth_nav.dat for ILSs. Just to verify, I edited the coordinates and heading in that file (made a backup) with the data from Navigraph and I can see the change in WED, and in the sim. The localizer is now placed at the correct location and is aligned to the runway centerline. This will fix my issue for the time being. I have already filed a bug at the scenery gateway to fix the ILS couple of days ago - but I hope it will get fixed with XPNAV1150. Thank you so much! 🙂

[JRBarrett 3,034]

4 hours ago, FltsimFlyboy said:

Ahhh... my bad! I did not realize that there was yet another earth_nav.dat for ILSs. Just to verify, I edited the coordinates and heading in that file (made a backup) with the data from Navigraph and I can see the change in WED, and in the sim. The localizer is now placed at the correct location and is aligned to the runway centerline. This will fix my issue for the time being. I have already filed a bug at the scenery gateway to fix the ILS couple of days ago - but I hope it will get fixed with XPNAV1150. Thank you so much! 🙂

You’re welcome! Glad the edit fixed it!

The scenery gateway is a clearing house for edited default airports, most of which have been modified / updated by X-Plane users with WED. As you may know, many airports, especially major ones like KJFK, EGLL etc. have been updated many many times - sometimes to add new or missing features, other times to correct reported errors. The curated localizer file has long been maintained by a gentleman named Robin Peel, who has done yeoman service for the XP community over the years, but errors like the one at VECC do occasionally occur.

I don’t know how long it takes for a correction to a reported ILS to make it into the next XP update, but I think the process is pretty fast.

Up until about XP 11.30, end users could modify default ILS systems themselves using the built-in map display, which used to have a an “edit” button. In edit mode, you could change the latitude, longitude, frequency, identifier, and course of any default ILS localizer. Edits made this way would get stored in a file called user_nav.dat that would override the curated localizer data on the computer where the edit was made.

The editing function of the map display was removed sometime after 11.30 - probably in anticipation of the upcoming XPNAV1150 change in the core nav data files.
 

[Michael Rempel 3]

You should look at the WED tutorials on Youtube.

Jan is really long winded, but he explains it all in detail. He also gives you instructions on how to get your WED update approved for X-Plane, and he seems to know a lot about the upcoming stuff in WED. There are lots of tricks and gochas to understand. As well he goes into some detail about limitations in X-Plane that a lot of people dont like. For instance, airport runways need to be flat. And you need to be able to taxi on them. I like mountain flying and finding a flat runway with a decent simple approach is often super hard. The reason to fly these is to work out the landing without pranging real hardware. You cant do that in the mountains with X-Plane. From what I understand the next release will be even worse. The presumption is also that all runways are well maintained. False in the mountains. Carry a small pick, shovel, and chainsaw for new spot landing, even if it looks fantastic from the air. If nobody knows about it, and nobody lands there, there is likely a good reason.

 

 

[Janov 2,383]

1 hour ago, Michael Rempel said:

Jan is really long winded

You should ask my wife about that! 🤣