Please Help Me with Airports on Hills !

I'm sure you know what I'm on about.

I have LOD set to 21 in FS9, and a bunch of airports - default/freeware and payware - are now set on little mountain plateaus.

Is there any way of adjusting the terrain around them, easily and quickly to smooth it - even if not realistic.

Or, do I need to reduce the terrain detail in-sim ?

Thnx inadvance as always.
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Hi there,

you'd have to create a Flatten Polygon with the height being closest to the height of the Hill / Mountain in question, this will then smooth out the terrain around the airport at you specify.

Programs like Airport Design Editor and FSX KML can both produce these Flatten Polygon's

I believe in FS9 you'd probably not be able to fix the airport plateaus like you would in FSX, you'd have to generate new mesh with tools that can allow you to blend your flatten into the underlying mesh to make things work nicely.
Thnx for that guys.

How exactly would I use ADE to flatten the area (or essentially, raise it) around the airport witohut actually creating a new airport ?

If the airport cannot be opened in aDE - which some can't - can I actually make a BGL jsut for the flatten polgons ? - and presumably activate it a higher level than the airport itself.

Thnx again.
Hi Gabe:

Could you post an attached screenie of an example airport that you'd like to "fix" ? ;)

As VADS stated, in some cases a (FS9 SDK LWM3-type) flatten BGL made with SBuilder for FS9 (or with ADE in FS9 mode) will do the trick in FS2004.


NOTE: Although somewhat similar in FS-rendered flattening impact on the underlying terrain, FS9 SDK LWM3-type flatten BGLs generated via BGLCompiler (aka "BGLC") or SCASM are not to be confused with "CVX vector" type flatten BGLs made with the FSX SDK via SHP2VEC.


Thus, "CVX vector" type flatten BGLs made with the FSX SDK will not work in FS9.

BTW: FS9 SDK LWM3-type flatten BGLs do work in both FS2004 and FSX, but their precision with which they are rendered depends on:

a.) The FS9.Cfg "TERRAIN_MAX_VERTEX_LEVEL=[x]" parameter setting

When [x] is a greater LOD number such as "21", more precision rendering of the flatten is allowed in FS2004 (..."if" flatten polygon BGL elevation source data points are "intended" to be rendered closer together).

b.) FSX terrain mesh slider setting (a higher mesh resolution=smaller distance in Meters between rendered mesh vertex elevation data points).

With a higher FSX mesh resolution slider setting, more precision rendering of the flatten is allowed (..."if" flatten polygon BGL elevation source data points are "intended" to be rendered closer together).

In other cases, as Dean (aka "Hollywood") points out, enabling greater terrain details in FS2004 via the FS9.Cfg parameter setting "TERRAIN_MAX_VERTEX_LEVEL=21" will reveal some airport location source data problems which, when rendered in FS, may manifest as airports on plateaus or in troughs.

IIUC, most often this mis-match between airports and surrounding terrain is due to an inaccurate reported airport elevation that ended up in the database that ACES (and all others including aviation mapmakers and independent FS developers) refer to for airport location info.

That reported elevation may be incorrect relative to the actual physical elevation of the terrain as determined via more accurate methods.

When "surveyed" terrain elevation data (that is more accurate than "reported" airport elevation data) is used to make a terrain mesh for FS, we may end up seeing the airport displayed ...either on a plateau, or in a trough relative to that underlying FS terrain mesh . :eek:

Efforts were made to minimize this issue in FSX by ACES and some 3rd party developers via "cutting out" the higher resolution (greater LOD number) data from higher-LOD and/or multi-LOD terrain mesh BGLs, so that when airport terrain renders, it does so at a lower LOD (...and therefore with a lower level or "number" of terrain vertices), causing the airport to blend into a surrounding area without plateaus / troughs that would otherwise be seen.

However, in FS this forcing the terrain mesh around the airport to display at a "lower LOD" in some cases could mean there is literally 6.079496 Miles (9.784 Kilometers) between terrain mesh elevation data points surrounding the airport flatten, as in some example 3rd party add-on mesh scenarios I have seen where the FSX terrain mesh rendering was intended to "fall back" to a LOD-2 resolution near some airports.

But in most cases, data would likely be rendered from the FS default system "dem4km.bgl", which IIRC in FS2004, actually contains elevation data points at 4.892 Kilometer intervals, since few FS9 3rd party add-on meshes contain LOD-2 data.

In FS2004 this would be the equivalent of setting a FS9.Cfg parameter of "TERRAIN_MAX_VERTEX_LEVEL=12", which would dramatically limit how much detail could be rendered from any FS terrain mesh BGLs installed and active in the FS scenery library.

IMHO, such a "global" setting would make FS look pitiful everywhere... just as it would make FS look pitiful local to the airport itself; it is therefore an unacceptable solution.

Again, IMHO, it would instead be preferable to make some "sloped flattens" with vertices extending outwards to the surrounding terrain from the edge of the main airport background 'single-elevation' flatten.

FYI: There is some information to be found searching for "sloped flatten" here at FSDeveloper and other FS forums, ex: :idea:

PS: Yes, IIRC, you'd want the "sloped flatten BGL" to be in a scenery library area layer above the airport in question AND any 3rd party add-on terrain mesh you have installed.

Hope this info helps ! :)

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