Hello:
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):
http://www.fsdeveloper.com/forum/downloads.php?do=file&id=68
http://www.ptsim.com/forum/viewtopic.php?p=752
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:
longitude
latitude
width
and POLYS were sets of XY points defined by:
longitude
latitude
Now POLYS are sets of XYZ points defined by:
longitude
latitude
altitude
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:
http://www.fsdeveloper.com/forum/showpost.php?p=233056&postcount=13
PS: Some other threads related to this topic which I've participated in:
http://www.fsdeveloper.com/forum/showthread.php?t=21545&highlight=sloped+flatten
http://www.fsdeveloper.com/forum/showthread.php?t=21981&highlight=sloped+flatten
Hope this helps !
GaryGB