FS2004 FS2004 cliffs and flattens

Hi all,

At the moment I am trying to blend in my airports with the new VFR Photographic Imagery for fs2004. When I put my airports in they match perfectly but there is a big issue with cliffs as can be seen in the image below.

Does anyone know how I can solve this to make the progression more natural?


With a new flatten, this seem to me that this is the flatten of the airport which extend till that zone. in your case shoould be easy make the flatten which sorround the aiport only.Open ADe and open the airport bgl file, do a new flatten polygon and compile.
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You need to make the area smaller, based of the height. If the height was only
15 feet, then the flatten can be almost the area you need. So make the area atleast 60% smaller then use the same height. This will give you a gradual slope.


A few questions:

  • What ICAO is that airport ?

  • Are you using any 3rd party add-on terrain mesh for that area ?

  • What terrain slider settings you using in the FS9 GUI ?

  • What is the TERRAIN_MAX_VERTEX_LEVEL (aka "TMVL") setting in your active FS9.Cfg file ?

IMHO, all this info would be important to know before deciding on what might be done with that apparent terrain "anomaly".

But, on a simple and practical basis though, it looks very likely that your flatten polygon for the ADE version of the stock airport approach and RWY is too long, and the terrain would normally slope off, beginning at the end of the RWY, but the extra long flatten is drawing the terrain back up to the level of the RWY.

If you shorten that approach and RWY flatten, you won't be as likely to see the terrain anomaly.

BTW: If after you shorten that approach and RWY flatten you still have an objectionable cliff or plateau effect at the edge of the RWY area, that would have to be dealt with via a "tilted" or "sloped" flatten to blend the edge of the airport background / RWY flatten into the surrounding terrain elevations.

AFAIK the only GUI utility available to make "tilted" or "sloped" flattens for FS9 is SBuilder for FS9.

SBuilder SBuilder_205, revision 6 for FS2004 (sometimes abbreviated as 'SB9' in forums):



Also, "Search" the SBuilder for FS9 help file (sbuilder.chm in the [Sbuilder install path]\HTML sub-folder) for the query string "tilted" to find this section:

"LWM tilted polygons

Flatten and Water LWM polygons referred so far are constant altitude polygons. We refer to these type of LWM polygons as LWM type 2 or LWM2 polygons. SBuilder 2.05 allows you to work with tilted polygons. We refer to these polygons as
LWM type 3 or LWM3 polygons. The following is an explanation about the use of tilted polygons adapted from a post on the PTSim forum.

Before Sbuilder 2.05, LINES were sets of XYZ points defined by:

and POLYS were sets of XY points defined by:

Now POLYS are sets of XYZ points defined by:


Important Notes:

a) point altitudes in polygons are ignored in all cases except in polygons of type LWM.

b) LWM BGLs are now generated with "Poly3()" style commands. Therefore they will not work anymore in FS2002.

c) when you generate a LWM mask you need to press "Change" in the altitude box in order to set the altitude. "OK" is not sufficient. The idea is to make the working with "altitudes in polygons" very similar to the working with "widths in lines".

Here is a illustrated example to create a tilted plane. You can use this for tilted runways or for LWM rivers that approach the sea (altitude is 0 when the river reaches the sea but not 0 when the river is far from reaching the ocean).

In the example I have a polygon with 9 points. I want Point 9 to have an altitude of 20 meters and point 5 to have an altitude of 60 meters. The line that contains points 9 and 5 makes an angle of alpha with the horizontal plane. I want all the remaining points of the polygon to belong to the tilted plane that passes through 9 and 5 and that makes an angle of alpha with the horizontal plane. Here is what I have to do:

I start by drawing a polygon in the normal way (yellow). Then I enter the properties page and define the type of the polygon to be LWM WATER. I enter an altitude of 50 meters which will be applied to all points as soon as I press "Change". I used the value of 50 as it is a value between the extreme values of 20 and 60 that I want to define for the 2 important points - point 9 and point 5!. Then:

I enter the properties of point 9 and I declare its altitude to be 20 meters as in this picture:

And then I do the same for point 5:

I skip the picture where I declare the altitude of Point 5 to be 60 meters and I show the what I get if I reenter the properties of the polygon. I go for the "Points" window which looks very similar to the one you get when you are setting widths in VTP lines. The main difference is that you set altitudes instead of widths:

The window shows the highest and the lowest point which is in accordance to the previous settings. Now if I press "Change" in the Progressive window, points 1 2 3 4 6 7 and 8 will get the altitude that places them in the target tilted plane.

That is all. Do not press "Change" on the left as it would make all points at 40 meters! Just press OK and compile to see the result.

NOTE: When using "tilted" or "sloped" flattens to blend the edge of the airport background / RWY flatten into the surrounding terrain elevations in either FS9 or FSX, it is important to decide what terrain mesh resolution you intend for your airport to be used with, because the terrain mesh "shape" may change with different factors.

Factors which may may change FS terrain mesh "shape" at run time include

1.) Internal resolution of terrain mesh BGL files ("density" of mesh expressed in Meters between elevation data points)

2.) TERRAIN_MAX_VERTEX_LEVEL (aka "TMVL") setting in your active FS9.Cfg file

3.) FS GUI terrain mesh complexity slider setting

4.) FS GUI terrain mesh resolution slider setting

FYI: For additional details on the impact terrain mesh resolution and "aliasing to quad matrix area points" may have on 'precision' of placement for vector content vertices (including "tilted" or "sloped" flattens to blend the edge of the airport background / RWY flatten into the surrounding terrain elevations)... see this thread:


PS: Some other threads related to this topic which I've participated in:



Hope this helps ! :)

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Excellent guys, thanks for thr replies. I think my best method is to use sbuilder to create a sloped flatten to get rid of these cliffs. I shall experiment over the weekend and report back.

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I created a flatten but it did not get rid of the cliffs. It was like the cliffs had a higher priority. How do I delete the long flatten that is been created on the runway approach?

Take into account what GaryGB say, with a "not work" is not enough, in Fsx normally there isn't an easy and fast solution. anyway I advice you to check the aiport height, and if match with ade height, second I'll give you this trick, make the flatten, directly from the bgl file of the airport, and rename with a different name, and delete the old cvx file,adjust the polygon of the flatten just around the runway and buildings, and if this show some kind of cliff make them sloped. and check if any other files are present in the scenery. usually you could find that there are duplicated airports even. and third, don't worry it is a minor problem easy to fix. and good flights.
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