The popularity of a recent upload to the File Library, almost 1500 downloads in two days - and no Forum posts about it, suggests that it is time for a brief note about mesh quality and use. The mesh in question was constructed from SRTM 3 arcsec (90m) source data using an LOD of 9, giving a final mesh resolution of 76.4m.There are two issues of primary concern here:1) Users - Mesh precedence determines which mesh you see in the simulator. Flight Simulator handles mesh differently from other scenery, and FS2002 and FS2004 each handle mesh precedence differently as well. Since the default mesh for the same area (in the USA) is also LOD9, you will probably never actually see this addon mesh. FS2002 resolves this conflict by assigning the higher precedence to the mesh constructed form the higher resolution source data. I see no difference in the terrain with the addon mesh active, and so assume the default mesh was probably constructed from higher resolution source data. FS2004 resolves this conflict by assigning higher precedence to the mesh in the scenery layer with the LOWER Priority if the conflicting mesh files are installed in different folders. If they are in the same folder, the filenames are used. If the addon mesh being discussed here is simply installed according to the directions included with the mesh, it will have a HIGHER Priority (when placed in the Addon Scenery folder) than the default mesh, and so will not be used by this FS version either. In both sim versions, you can force this addon mesh to be used. I did this with FS2004, and the mesh is different from the default, and quite different from my own 10m mesh for the same area. (I have to wonder if the developer ever saw his own mesh; if so, why did he provide an installation routine that guarantees that users relying on it will not see his mesh?)2) Developers: Much better data is available for the US. SRTM data is available in 1 arcsec resolution, and is generally preferred to the much lower 3 arcsec data used in this case. But much cleaner seamless 1 arcsec data is available from the USGS (along with a great deal of 1/3 arcsec data and even some 1/9 arcsec data as well). The sophistication of the techniques used to fill holes caused by missing values in the SRTM data do not compensate for the low resolution of the data. For example, 1/3 arcsec data has 81 elevation points for the same area represented by a single elevation point in the SRTM 3 arcsec data (and there are usually no missing values). There is simply no comparison when it comes to accuracy. So the only justification for using SRTM data for US mesh is the fact that you do not know how to make mesh any other way. This is fine for personal use, but please, reconsider before making such mesh available to others. Then check your new mesh with TmfViewer to confirm that you have actually created real mesh (not all mesh uploaded to the library actually qualifies as mesh at all!). Finally, provide installation instructions/procedures that will insure that users will actually see your mesh. Good addon terrain mesh can add a great deal to the flight sim experience. If you see no improvement with your new mesh, a little bit of additional knowledge may be needed. Here are some relevant links on my website that can help:http://www.fs-traveler.com/resources-g.shtml(includes two text files describing the resolution of the default mesh in FS2002 and FS2004 - a good place to start)http://www.fs-traveler.com/priority.shtml (how FS determines the mesh precedence - so your use of mesh is not left to chance)http://www.fs-traveler.com/products-f.shtml (free sample mesh that WILL make a difference)Regards,Steve

Great post Steve. As with the FS9.cfg file there is a ton of misinformation posted all over the place, it might be good to also add to your post the accurate information concerning the limitations of FS9 in displaying LOD values of mesh add-ons as compared to FS8 as well as the what, why and when to changing the "TERRAIN_MAX_VERTEX_LEVEL=xx" value in the FS9.cfg file.

I have to agree that it does seem somewhat strange to play with SRTM 3 data for the USA, other than as a learning experience. Unless I am missing something? Isn't there better NED data for most areas outside of Alaska?scott s..

>Great post Steve. >>As with the FS9.cfg file there is a ton of misinformation>posted all over the place, it might be good to also add to>your post the accurate information concerning the limitations>of FS9 in displaying LOD values of mesh add-ons as compared to>FS8 as well as the what, why and when to changing the>"TERRAIN_MAX_VERTEX_LEVEL=xx" value in the FS9.cfg file.Setting this value above the default "19" on my system caused alot of "pop-up's" in the distance.See you in the fence...CYYZ

To add to the flaws of SRTM:The SRTM data measures actual elevations, NOT terrain elevation. In built-up areas or forested areas, the elevation in SRTM will be higher than the actual terrain. This of course leads to artifacts. In most cases SRTM is better than nothing, but if a non-SRTM mesh of similar resolution exists, chances are it'll be better.Cheers, Christian