As part of my work on doing full 3D building support, I found that I needed to change the globe model to be more accurate. Previously, I was using a simple sphere, and so altitudes were simply heights above that sphere. The Earth, of course, is an oblate spheroid, an ellipse with an imperfectly curved surface.

So now it is in Metabunk too. It uses the EGM96 geoid, which is basically a map of the altitude of the geoid (essentially the local sea level) relative to the WGS84 ellipsoid.

3D buildings are still a WIP, and disabled for now (and will likely be limited), but the ellipsoid is in there. You can turn it off in the Terrain menu, which you shoud try if you have problems.

There almost certainly will be problems, but I've spent many hours trying to ensure there won't be. Likely issues will be altitudes being wrong, or positions being slightly off. Let me know!

Benefits are that things like ADSB tracks should be even more accurate now (errors of about 100 feet were possible before, depending on the track source. EGM96 from ADSBx being one). Also Starlink positions and flares should be slightly better.

If you are really interested in the technical details.
https://www.metabunk.org/sitrec/docs/GIS.html