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Hirgab

Airport Elevation

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I noticed a strange thing yesterday at two default African airports, where the entire airport area was either +/- 100 ft higher or lower than the immediate surrounding area. Cairo Intl was on a high plateau to its surrounding and Addis Ababa Airport was on a much lower plateau. I am using FSGenesis for a mesh program, I was trying to find real pictures of the airport and I did for the latter, and noticed that it is not on a plateau! Any help is appreciated. Thank you.

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What you are seeing is the difference between what FSGenesis considers to be the elevation around the airport and what Microsoft considered to be the elevation. The proper way for FSGenesis to have done their elevation would have been to properly alter the terrain in the area of the airport; but this is very time consuming when one considers how many airports would have to be adjusted. This is one of the reasons why Orbx scenery is so popular; they make sure the mesh elevations are correct at all the airports in a region before they release it!Regards, Mike Mann

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FSGenesis and ORBX terrain mesh elevations points are 76m apart in Africa, versus Microsoft's default which is a whole kilometer or more. This means that FSG/ORBIX terrain mesh is of much higher resolution than the MS default terrain mesh and, hence, more accurate. With the wide distances between elevation points with default terrain mesh the ground appears much flatter than it would be if higher resolution mesh was used. Entire hills, peaks, valleys, and troughs go missing with MS default mesh, and the airfield elevation is set to merge with the default mesh, not it's real-world elevation. The airports maintain their MS default elevation when you install high-resolution mesh, and that's how you get some airports sitting on high, isolated plateaus or sunk deep in isolated gorges. For instance, if you have high-res mesh for Alaska, take a look at the default airfield at Dutch Harbor. It's a hilariously extreme example of this situation! Confirming what mman stated, the only way to correct this issue is to edit each airport individually so that it matches it's real-world elevation, a very time-consuming process. Moreover, most real-world airport runways aren't on perfectly flat ground, so the runway - and the rest of the airport property - would actually dip and rise with the terrain. Unfortunately, airports in FSX are rendered on perfectly flat ground, so even if the airport elevation itself is accurate, edges of the airport may still seem to either rise or fall away from the surrounding terrain. Again, the only way to correct this is to manually edit the immediate surrounding terrain elevation around the airport so that it blends in more naturally with the whole airport. This is also a very time consuming process. This is something we simmers have lived with for years in FS9 and FSX...

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One thing to be aware of is that a higher mesh resolution doesn't necessarily result in a more accurate elevation at a given point. I recently removed a plateau at the Toad River/Mile 422 (Alaska Highway) Airport (CBK7) in British Columbia. The interesting thing is that the elevation for this airport on the charts is 732 meters, Microsoft placed it at 731.520 meters and to get it looking fairly close with FSGenesis mesh enabled, I had to place it at 711.520 meters! So Microsoft has the more accurate mesh at the airport location.On the other hand the Natural Resources Canada 1:20000 Topographic Map shows the elevation closer to what FSGenesis did; but the Topographic Map also shows the airport about 3/4 of a kilometer too far west! FSGenesis isn't the only one that has a problem with this area; Ultimate Terrain X Canada placed the Alaskan Highway too far west by about 3/4 of a kilometer (guess they were looking at that same Topographic Map) and consequently they didn't have room to place the fairly large body of water called Reflection Lake so they completely left it out!As with anything else in this world garbage in, garbage out, the only solution is using a large number of sources and cross-reference them and hopefully come to some consensus.Regards, Mike Mann

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