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Guest ocelotl

SRTM-30 Mesh LOD

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What exactly the best LOD for compiling a SRTM-30 data;LOD 11, LOD 10, LOD 9 or LOD 8?Mardley.

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SRTM30 has 30 arcseconds (~1000m) of horizontal spacing, then LOD5 (1223m) is the closest LOD and possibly the best choice.

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Emerson is right, although you may see unreal bumbps on your mesh due to the slight undersampling of the reference data. Most of the people I've met prefers visually the LOD6 version of SRTM30 than the LOD5.

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But what exacly the different if LOD9 or LOD10 is use, and I saw most mesh scenery designer use LOD9 or LOD10, and some commercial use higher for this SRTM-30 data, as I am understand that the higher the LOD means gives more detail but consumes more space.

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Let me try to explain it to you.Steve Greenwood explains it better on his site, http://www.fs-traveler.com/ but I'll try to discuss it here.SRTM-30 data is a reference data that is more or less the same resolution as the LOD5 resolution data uses by Microsoft for default mesh terrain data for most of the world.Using SRTM-30 data to generate LOD9 or LOD10 simply means that you will be oversampling data to get terrain, so you wouldn't be actually improving the mesh terrain you're using on MSFS.To produce detailed mesh terrain data from real world origin, you have to get more defined data than what is available from SRTM-30.Free data that you can get and that is better than SRTM-30 is:SRTM-3 data, where the spacing between points is 3 arcseconds or roughly 90 meters. This data is best processed to get LOD9. A warning: There are lost areas, spikes and noise within most of the blocks comprising SRTM-3, so this data needs to be processed in some form prior to be converted into BGL with the MSFS scenery tools.SRTM-1 data, available only for U.S. territories and possesions is arcsecond spaced data (roughly 30 meters), and has the same warnings as SRTM-3. This data is best processed to get LOD10.You can get SRTM data from ftp://e0mss21u.ecs.nasa.gov/srtm/Best utility to process it is MWGraphics from Martin Wright for 3 arcsecond data, and other good ones are SRTMtoBGL and if you want to do it all by yourself, you have to get freeware GIS processing software, like Microdem or Blackart, then transforming it to raw 16 bit data and generating your own .inf files to process the data with resample.Some data that needs thorough processing to be usable is STDS, available only for US continental territory, has 30 meter spacing between sampling points and in several areas 10 meters between points, the higher resolution makes it possible to generate LOD12 terrain (I generated scenes for the Meteor Crater and Devils Tower using 10 meter STDS, and have them somewhere), but needs the following since the data is not on the WGS84 standard used by MSFS sampling and presentation modules:- Collecting needed STDS blocks, each covering a 7.5 by 7.5 arcminute quadrangle.- Merging the quadrangles to get the intended area (Best with Microdem)- Resampling them from their native UTM projection, datum NAD27 or NAD83 to WGS84 geographic projection, resampling it accordingly (1/3 arcsecond for 10 meter data and 1 arcsecond for 30 meter data)- Generating a raw or BIL DEM to be used with resample- Generating a .inf data file to make the processing.Hopew it clarifies your doubts.

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