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Where are airport flatten elevations derived?

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Thanks again, Dick.

IIUC, Airport2Project_1_0_0_20 does not interpret an Airport Boundary / Background Polygon in your HGLH project attached above.

Can you create an 'airport flatten' at HGLH ...so we can use BGLViewer to see where / how SU9 codes Airport Boundary "Flatten" Polygons ? :scratchch


Thanks in advance for sharing any additional insights you may have regarding this aspect of the SU9 et seq. updated coding. 🙂

GaryGB

Just a heads up on my post regarding Airport2Project_1_0_0_20 functionality ...that I posted in the BGLViewer thread. :pushpin:

https://www.fsdeveloper.com/forum/threads/bglviewer-for-fsx-bgl-files.432840/post-902469


GaryGB
 

rhumbaflappy

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I think the airport flatten is in the airport definition... not as a polygon.

applyFlatten="TRUE"

BGLViewer shows this:
Untitled.png

And that is the flatten, as far as I can tell.
 
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Hi Dick:

That certainly merits further inquiry, but I wonder if it may be a On / Off switch for flattening within (Kilometers of) a ARP Test Radius ? :scratchch

https://www.fsdeveloper.com/forum/threads/project-saving.454364/post-902261


AFAIK, this is the MSFS default flatten for C59:

[MSFS-2020_Packages install path]\Official\OneStore\fs-base-genericairports\scenery\0302\CVX2416.bgl

c59_msfs_default_flatten-0302-cvx2416-jpg.81938


https://geohack.toolforge.org/geoha...38_02_N_088_36_04_W_region:US-WI_type:airport


If I:

* Use CvxExtractor to output a *.BLN

...and:

* Search the *.BLN in NotePad / NotePad++ for -88.601 Longitude

...I find C59 area vertex coordinates in this CVX vector "Polygon" object:

Code:
5,1,AirportBounds_428_0
-88.6062526702881,42.6308423280716,0
-88.606231212616,42.6307511329651,0
-88.6045217514038,42.6307564973831,0
-88.6045217514038,42.6308584213257,0
-88.6062526702881,42.6308423280716,0

Does the "0" value in the Altitude field of those records mean 'fallback to the assigned ARP Altitude for the entire test radius' ? :rolleyes:

GaryGB
 

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Hi again:

To compare MSFS and FSX C59 FS Airport Boundary CVX Flattens, here's the CVX-FLX-derived SHP files in Global Mapper: :pushpin:

MSFS

c59_msfs_default_flatten-0302-cvx2416_gm-jpg.81939


FSX

c59_fsx_default_flatten-0302-cvx2416_gm-jpg.81940



Has no one yet identified exactly where and how MSFS Airport Flattens get an assigned Altitude value if CVX Altitude = '0' ? :oops:

And if it is from ARP Altitude in the "Airport XML", when 'ApplyFlatten' is enabled, is the Altitude value only used by Flattens ?

If so, are all Flattens in a circular area surrounding the airport within the extent of a Airport Test Radius ...assigned ARP Altitude ?


BTW: FSUIPC Reports...

MSFS C59 RWY-18 Altitude: 299.990176205523 Meters AMSL
MSFS C59 RWY-36 Altitude: 296.061154319439 Meters AMSL

...thus, the run time MSFS default C59 RWY is sloped.

IIUC, MSFS CVX vectors with an Altitude field value of "0" ...are falling back to local ground isoline elevation data (in CGL files ? o_O).

But what Altitude is used, and where / how is it used with 'Terraforming Rectangle' objects ...when "ApplyFlatten" is enabled ?

https://docs.flightsimulator.com/ht.../Objects/Airport_Objects.htm?rhhlterm=Flatten


"Apply Flatten

Checking this option will auto-generate terraforming rectangles within the bounds of the airport test radius to flatten the terrain. These rectangles are internally defined and not rendered in the world as objects, although their effects will be visible on the terrain."

< Where exactly do we find this code, assuming we can de-compile / output it into XML / ESRI SHP files ? > o_O

Related SDK links:

https://docs.flightsimulator.com/ht...perties.htm?rhhlterm=Flatten&rhsearch=Flatten

https://docs.flightsimulator.com/ht...m?rhhlterm=ApplyFlatten&rhsearch=ApplyFlatten


IIRC, past ADE versions normally included FS' default vector for Airport Boundary Fences in the 'derived' project code.


If we compare FS' default vector Airport Boundary Flattens in (legacy FS) CVX-derived project code, Flattens match (Airport Boundary) Fences.


If working with ADE, would we otherwise be compelled to use an external work-flow (ex: CvxExtractor XML output) to:

* de-compile FS' default vector objects for Airport Boundary Fences / Flattens in 'derived' project code and output XML code

...then:

* Import XML (this feature is obviously 'missing' from ADE 2020 Alpha 2021 et seq.) :banghead:


...to successfully display / edit / output FS' default vector objects for Airport Boundary Fences and Flattens via the ADE GUI ?


BTW: I see ADE 2020 Alpha 2021 Project Tree lists a SHP Poly, but no Terrain Polygon ...if "Add Polygon" makes a new Flatten.


How does a SU9 Flatten "Polygon" affect MSFS' default Flatten CVX vector rendering, and does it work via "Apply Flatten" ?


PS: To compare MSFS Isolines with NED 10m grid, 1 Meter Contours at C59 , here's some screenshots from MSFS and Global Mapper:

MSFS

c59_msfs_default_isolines_1m_contours-jpg.81941


FSX

c59_msfs_default_flatten-0302-cvx2416_gm_1m_contours-jpg.81942


GaryGB
 

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rhumbaflappy

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The CVX flattens are the old shapefile style flattens. I don't believe Asobo will ever make them as the new style.
BGLViewer is just reporting the values using the old FSX terminology. So that can be misleading. The poly in question is not an AirportBounds in MSFS.

BGLViewer_01.png


But there may be some commonality between what FSX meant and MSFS means. Altitude Type = SameAltitude. Maybe this means the same altitude as the reference point (initial point of the poly, which is how elevation is derived in MSFS polys). Common Altitude may mean all points are the same. This is all just a guess.
So from where is the altitude of the initial point derived? Could be runtime, grabbing it from the ground elevation. Or it could come from the Airport elevation of 296.57 meters (but that seems unlikely to me). Or is the elevation hidden in the code somewhere?
I'm not sure any of this matters. We can change or exclude polys as we like in the sim.

This seems to be the equivalent XML poly:
XML:
    <Polygon altitude="296.57000732421875">
        <Attribute name="UniqueGUID" guid="{359C73E8-06BE-4FB2-ABCB-EC942F7761D0}" type="GUID" value="{89417447-1F01-4218-B0EB-5988EE6ED128}"/>
        <Attribute name="FlattenFalloff" guid="{5548FDB5-2267-4328-8E6F-FD0A45ADEC8F}" type="FLOAT32" value="1.000000"/>
        <Attribute name="FlattenMode" guid="{065E9D4D-6984-4D2A-91FD-3C33C4F53B22}" type="UINT8" value="1"/>
        <Attribute name="LandClassRemap" guid="{0A685EB0-0E01-44FE-B9EF-BFFFBC968ADE}" type="UINT8" value="2"/>
        <Attribute name="Layer" guid="{9E2B4C3E-7D84-453F-9DCC-B6498FF46703}" type="UINT32" value="1"/>
        <Attribute name="AirportSize" guid="{86A147E9-ACF2-4780-9D3C-416373ECB451}" type="UINT8" value="2"/>
        <Vertex lat="42.64016568700000" lon="-88.60088825200000"/>
        <Vertex lat="42.62799382200000" lon="-88.60205411900000"/>
        <Vertex lat="42.62797772900000" lon="-88.59951496100000"/>
        <Vertex lat="42.62907743500000" lon="-88.59913587600001"/>
        <Vertex lat="42.64026761100000" lon="-88.59995126699999"/>
        <Vertex lat="42.64016568700000" lon="-88.60088825200000"/>
    </Polygon>

Note, I entered 296.57 as the altitude, but saving from the sim changes it to 296.57000732421875. Verticies were changed slightly as well. This means that DevMode is snapping the verticies to it's grid system. Entering the Polygon without an altitude seems to be the same as 0.0
 
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Many thanks Dick, for posting your clarifications and impressions; it has answered a number of questions I had. :)

It will prove interesting to see how the "Terrain" aspect of MSFS evolves relative to "Airport" coding as the SDK is developed further. :coffee:

As I explore this more, should I have additional inquiries specific to this sub-topic, I shall likely follow up by posting them in this new thread. ;)

GaryGB
 
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