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:
The correct (and current) AIRAC data is being recognized by the aircraft FMC/GPS - this means it is picking up the Navigraph data.
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.
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.