FMMI elevation problems


The inaccurate FSX / P3D default terrain mesh is 1000 Meters too high relative to the real word for that part of Madagascar.

IMHO, the only practical solution is to use a 3rd party terrain mesh replacement BGL(s).

I would recommend using the 30 Meter (1-Arc-Second) FreeMeshX:

FreeMeshX – Global 2.0 (46.1 GB)

Using uTorrent, during file transfer, you can select to download only the files providing Geographic coverage for Madagascar.

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Thanks for the info Gary,
I installed FreeMeshX for Africa which include Madagascar but I still have these Huge Hills around FMMI Airport

Hi again:

Verify that you have set the Airport Reference Point (aka "ARP") Airport Background / Boundary Polygon Flatten (aka "ABP"), RWYs, and Taxipaths all to the same Altitude in Meters AMSL for FMMI airport as cited here:

Elevation AMSL 4,198 ft / 1,280 m

Install Google Earth Desktop Edition:

...Then double-click on this link to Ivato_International_Airport:

...and allow it to open in Google Earth, so you can see local elevations for water bodies and the airport infrastructure itself. :pushpin:

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Hello Gary
I checked the original afcad file in ADE the airport reference data is 1279.550 meters or 4197.999 feet, the runway is at the same altitude
I looked in google earth, airport is 1268 m and surroundings are between 1248 and 1270 m

I don't understand what i am supposed to do now to get rid of theses huge hills which do not exist in reel life.

Do i have to create a polygon to flatten it in ADE and if yes, how do i do that ? there are many possibilities of polygon in ADE and I never used that fonction.
Hi sanook:

Blending the 'central' airport Airport Background Polygon into the surrounding terrain can be a complex process if one wishes to achieve a result which is visually satisfactory at lower altitudes in the user aircraft.

FS Airport Reference Point (aka "ARP") Airport Background / Boundary Polygon Flatten (aka "ABP"), RWYs, and Taxi-paths must be all set to the same Altitude in Meters AMSL for FMMI airport in order to maintain compatibility with default AI / Ground Vehicle traffic.

This results in a flat and 'level' airport terrain surface that inevitable will cut into surrounding terrain that is higher than the ARP, and will drop off into surrounding terrain that is lower than the ARP.

Assuming you wish to also maintain compatibility with default AI / Ground Vehicle traffic, technically you could keep the 'central' ABP smaller as seen in your screen shots above, and attempt to make a number of Triangular "sloped" flatten polygons which have bases that extend from the vertex points of that 'central' ABP outwards to form apex vertex points at altitudes that align more aesthetically with the Altitude of surrounding terrain mesh.

This must form a flawless Triangulated Irregular Network (aka "TIN") to optimize run time performance, and to avoid anomalies (ex: voids, pits, spikes etc.) within the local FS terrain surface, and can be very laborious to do manually. :alert:

IMHO, a more practical approach is to extend the 'central' ABP itself farther outwards to form apex vertex points at altitudes that align to the Altitude of various landmarks on the surrounding terrain mesh. :idea:

And IMHO, this might be less laborious and may yield a result which is more visually satisfactory at lower altitudes in the user aircraft, when it is performed in SBuilderX- rather than in ADE- especially if you intend to use custom photo-real imagery textures in the vicinity of FMMI airport.

This would allow you to identify outer edges of landmarks such as paved areas at the perimeter of the airport ex: along roads, and nearby undeveloped drainage areas etc. ...where more abrupt Altitude changes in terrain might be made less obtrusively.

This process might be more efficiently and accurately performed using a GIS application such as Global Mapper or QGIS, and alternatively via Terrain Sculptor Pro by Don Grovestine (aka "gadgets"), these each have their own complex learning curve and may involve some financial expense.

It could also be done in a 3D modeling application such as Sketchup, which, after accurately merging the several 1-Kilomter sized areas, can be imported to Arno's ModelConverterX (aka "MCX") ...and exported as a FSX "sloped flatten' BGL.

To pre-visualize what you may have to work with, you can use SDK TMFViewer to open

* [FreeMeshX Global 2.0 install path]\\FreeMeshX - Africa\scenery\S20E040.bgl

* [FSX install path]\Scenery\0704\scenery\cvx6038.bgl (or your own custom local CVX vector BGL ...if already made)

* Your own local custom photo-real imagery BGL (...if you have already made one)

NOTE: The "Value" seen on TMFViewer bottom status bar is FS' terrain mesh Altitude in Meters from the S20E040.bgl

Generally speaking, one could freely use either SBuilderX (or ADE) ...along with a concurrent flight session in Slew mode, so the user aircraft can be moved to target land mark positions on the terrain mesh BGL 'intended' to be used with your FMMI airport scenery.

The target land mark positions for Triangle apex vertex points on the terrain mesh BGL can be read from FS' own internal run time data values for Geographic coordinates and "Ground" Altitude by SBuilderX (or ADE) via FSUIPC, and entered into the data dialog for the vertex points of your "sloped" flatten CVX vector ABP 'flatten only' object(s).

FYI: CVX vector ABP 'flatten only' object(s) are APBs without any ExcludeAutogen and/or MaskClassMap attributes.

These can be compiled into a BGL which will modify any terrain mesh BGL used with your custom airport "sloped" flatten BGL.

An example of how this may be done is here:

Note that a significant advantage to doing this in SBuilderX is the ability to work within the context of a concurrently displayed FS terrain quad grid in QMID and/or LOD, on top of a continuously zoom-able / scroll-able / pan-able imagery background.

Your existing custom airport central and "sloped" flatten BGL data can be 'Appended' (imported) into the SBuilderX work-space after being decompiled by Patrick Germain's CvxExtractor and output as ESRI *.SHP files.

BTW: Other local default or custom CVX vector objects may also be 'Appended' to your SBuilderX project (via that same process above_ assist with visualizing / modifying local scenery content. :pushpin:

Let us know how you wish to proceed with making a "sloped" flatten to blend your 'central' ABP into surrounding terrain:



* SBuilderX

...and perhaps some kind soul(s) may offer more detailed info here on how to proceed. :)

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Again thanks for your answer Gary.
As FMMI is not my home base and I just want to fly there from time to time I will choose the more "easy" ADE way even is the result is not perfect. I don't want to fly VFR around the airport as I fly mostly jetliners.
What I want to achieve is just a decent look when approaching or taking off from FMMI without these huge spikes which do not exist at the reel airport.
Hi sanook:

Please tell us whether you have already made your own custom local CVX vector BGL for a 'central' airport ABP at FMMI airport, or if you instead plan to just use the FSX / P3D default 'central' ABP flatten at FMMI airport already provided by: :scratchch

[FSX install path]\Scenery\0704\scenery\cvx6038.bgl

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Hi again:

I had one of my Beta Testers do some testing of the P3Dv4.x default terrain. and he also saw the anomaly.

BTW: P3Dv4.x' local FMMI dem0704.bgl terrain mesh file seems to be identical to FSX' default (....but with a newer date):

* 76 Meters between elevation data points (...or smaller numbers of Meters between elevation data points)


* LOD-2 through LOD-9

[P3Dv4.x install path]\Scenery\0704\scenery\dem0704.bgl

FYI: When P3Dv4.x Mesh Resolution slider is set to a 'higher' setting than internal resolution of that local terrain mesh BGL:

* 76 Meters - or a smaller number of Meters between elevation data points

...'cliff' anomalies begin to show.

When P3Dv4.x Mesh Resolution slider is set to a 'lower' setting than internal resolution of that local terrain mesh BGL:

* 152 Meters - or a larger number of Meters between elevation data points

...'cliff' anomalies no longer show.

While this raises questions as to why FSX does not show the same anomaly with what AFAIK is the same dem0704.bgl, it merits mentioning that no other P3Dv4.x mesh-related parameter change that was tested would eliminate the anomaly.

Perhaps this is evidence that L-M did not use a LOD "cut-out" method around default airports in P3Dv4.x terrain mesh ? :scratchch


This anomaly may be related to "oversampling artifacts" by the FS terrain rendering engine, and may be due to the fact that dem0704.bgl has an internal 76 Meter resolution, but the terrain slider is set to 'enable' a higher resolution without actual higher resolution elevation data points being made available by a terrain mesh BGL (this was noted in earlier versions of FS):

PS: Here are some prior discussions on the sub-topic of airport blending "sloped flattens" and methods to implement them:

* Lance Tucker (aka "LCSims" ? / aka "NoNewMessages" ?) alludes to ACES' use of a LOD cut-out at FSX default airports ?

NoNewMessages said:"

November 8th, 2009, 08:34 #23


Originally Posted by Crusader

The plateau I refered to . I'm going to continue to adjust my mesh settings within FSX but if it is a Addon Mesh problem there is probably nothing I can do to correct it . I've actually gotten use to it . LOL The surrounding terrain is beautiful . (Just don't bother the bears!). Maybe someone using FSG Mesh Vers2 can take a few pics and see what they end up with .​

Disclaimer: I develop and market products that contain addon mesh, but my comments are not intended to be of a marketing nature.

No adjusting of mesh settings will affect what you are seeing and I'll try to explain in as few words as possible. Default terrain around airports is at 1km resolution. For the metrically challenged, that's about 3/4 of a mile between data points. That's why there are no plateaus around default airports. Addon mesh, even of the same resolution as the default CONUS 38m, will override this 1km area and introduce visual anomolies.

An incorrectly placed airport or one that is at an incorrect elevation will only worsen the plateau effect that addon mesh can cause. Probably 80% of the airports are incorrectly positioned or elevated. One "solution" offered is to cut holes into a product to let the default 1km mesh show through, but this only works when an airport is at it's proper place and elevation. Thus for about, oh say 80% of the default airports, this will not work.

If Ed needs some addon mesh to work with, I'll be happy to obligize with some links.

As a customer of one vendor's product, I was disappointed that so many of the fields I would fly to were never "fixed". I know why that is and why that offered opportunity.

I believe I have parsed my words very carefully, but I do want to say the more informed the customer can be the better their decisons. There is more I *could* say, but I will leave it at Buyer Beware when it comes to addon mesh products."
GaryGB said:

November 10th, 2009, 06:31 #33


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Posts 221

Hi Olaf:

I just looked at the Raimondo Taburet add-on "10m_mesh.bgl" for FSX in the [Taburet Ranger Creek install path]\Scenery folder via FSX SDK TMF Viewer.

That file does NOT contribute any terrain data to Ranger Creek for an approximately LOD 11 sized area surrounding that location due to a "mesh cut-out" as described by "LCSims" above.

Thus one might conclude based on the info you provided above, that rendered terrain "anomalies" seen at Ranger Creek on your FSX configuration are likely the result of elevation data provided by your higher "10 Meter" (9.6 M) internal resolution FSG V2 add-on terrain mesh.

But more likely, FSG V2 mesh is depicting the "real world" terrain morphology accurately ...compared to what FSX default mesh can provide there.

On your FSX configuration, when Ranger Creek is rendered by FSX with the FSG mesh loaded, it apparently still retains the existing "real world" terrain morphology, and has NOT yet been "modified" in the FSG V2 release to "cut a hole out" around that airport; so the local terrain morphology seen is due to FSG's mesh (which is based on higher 10 Meter resolution source data).

The Taburet mesh provides NO terrain elevation data any closer than 1-1/2 LOD 13 quads to any side of the airport (the size of its "cut-out"); so the local terrain seen is the FSX default (which is based on lower 38 meter resolution source data).

It is also apparent that the "10m_mesh.bgl" Taburet "cut-out" has allowed FSX to fall back to rendering terrain mesh elevation at a FSX LOD-2 level in the "dem0101.bgl" file, as we do see the following change in elevations between coordinates (aligned) along Ed's RWY Positions, logged via FSUIPC at FSX-rendered "ground" level: :iidea:

* Holger explains use of "sloped flattens" at airports:

26 Mar 2013 #18

Hi Darren,

if you load the file ADE_FTX_ENG_EGBG_CVX.bgl, in \ORBX\FTX_EU\FTX_EU_ENG_05_SCENERY\scenery, into TMFViewer.exe, you can inspect our version of the sloped flattens at EGBG. These were manually placed in ADE, along with similar ones for more than 180 airports in FTX ENG. In other words, it may be tedious to place sloped flattens in this manner but it's not hard once you have figured out a workflow.

When I place sloped flattens (I didn't make those for FTX ENG and actually prefer SBuilderX) I turn off all autogen, slew around the airport along the surface to check how far out each sloped flatten polygon should reach, and use TCalcX to read out the local altitude for each polygon vertex. Other people use other approaches meaning you just figure out what works best for you.

The alternative approach is to use Global Mapper or similar GIS tools to blend you main airport flatten (platform) into your terrain mesh file, which is actually the approach ACES used for many of the default airports. The drawback is that you don't have fine control over the gradient of the surrounding slopes unless you go really fancy/complex and use more than a single fixed blending distance.

Cheers, Holger

An example airport blending "sloped flatten" seen in SDK TMFViewer from an end users FTX 'Scotland' scenery package:

[FSX install path]\ORBX\FTX_EU\FTX_AA_EGPB\scenery\cvx_ORBX_EGPB_Flatten_ST.BGL



Hope this info helps ! :)

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