Hi Bernardo:
The basic procedure we are often compelled to follow with terrain polygons is "
Remove and Replace".
You must exclude FS' default SPJJ Airport Background / Boundary polygon to remove the "
airport on a plateau" anomaly:
http://www.fsdeveloper.com/forum/threads/flatten-and-exclude-airport-background.344094/
http://www.fsdeveloper.com/forum/threads/default-airport-background.438294/
https://www.google.com/#q=site:www.fsdeveloper.com+exclude+default+airport+background
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EDITED]
Your SPJJ Airport objects, as well as Airport Background / Boundary exclude polygon(s) can be made with ADE connected to FS to log vertex coordinates and altitudes.
* Airport objects objects may all be contained within (1) BGL compiled by FSX / P3D SDK BGLComp
* CVX vector objects may all be contained within (1) BGL compiled by FSX / P3D SDK SHP2VEC.
CAVEAT: Elevation of the SPJJ RWY center at
12,414.66 Ft. / 3784 Meters in FS default terrain mesh:
[FSX install path]\Scenery\0304\scenery\dem0304.bgl
...is
higher than the real world elevation at
11,034 Ft / 3,363 Meters of same by
1,380.66 Feet / 420.8252 Meters
https://en.wikipedia.org/wiki/Francisco_Carle_Airport
I would suggest doing the exclude first; and
after having successfully removed the default SPJJ Airport Background / Boundary exclude polygon(s) with the underlying terrain mesh displayed as you wish using FreeMeshX,
then consider making the replacement SPJJ Airport Background / Boundary polygon in (2) sections:
* Central area of the airfield only (
required so that AI traffic / ground vehicles and G-Polys will work properly)
* Peripheral area '
surrounding' the flatten polygon for the Central area of the airfield (a 'terrain 'skirt';
optional)
NOTE: This would normally be made as a "sloped flatten" consisting of multiple polygons (triangles) in which the vertices match the altitude of the flatten polygon for the Central area of airfield where they adjoin it, then the Peripheral vertices match the altitude of the terrain mesh where they adjoin that surrounding ground surface.
FYI: This latter peripheral "sloped flatten" may
not be required if you
only need to flatten the Central area of the airfield so that AI traffic and ground vehicles will work unimpeded, and G-Polys can be draped onto the underlying flat ground surface.
BTW: If available aerial imagery is LOD-17 or higher, and of good quality, you may not even need to use G-Polys.
Once the underlying terrain mesh is displayed in FS as desired using FreeMeshX, with ADE connected to FS to log vertex coordinates / altitudes, create a new water polygon at an appropriate Altitude which matches the local terrain.
PS: Be certain to work only from any "non-hidden" vector data sets in your *.AD4 file and
replace entirely the
SPJJ_ADEX_BG_CVX.bgl you linked above, since it contributes an un-wanted very large "flat" flatten which causes the other 'clipped' terrain drop-off anomaly seen in your screenshot; that "flat" flatten polygon is the one for which you may- or may not- wish to substitute a "sloped flatten".
If you 'open' the KMZ file attached below in Google Earth (stand-alone 'desktop' application), you will see your custom "flat" flatten polygon from
SPJJ_ADEX_BG_CVX.bgl, ...within the context of aerial imagery.
https://www.google.com/earth/download/gep/agree.html
Note that this "flat" flatten polygon in your custom CVX vector
SPJJ_ADEX_BG_CVX.bgl has an additional impact on the local terrain 'shape' which is separate from that imposed by the visible flattened default water polygon contained within:
[FSX install path]\Scenery\0304\scenery\cvx2736.bgl
...which requires its own separate "specific exclude" and replacement CVX vector object procedures.
[
END_EDIT]
Hope this helps with your troubleshooting process !
GaryGB