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Creating free 1/3 arc-second mesh for US and need some guidance

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7,443
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us-illinois
Hi Chris:

This is the info on the USGS 1/3 Arc-Second (~10m) seamless elevation data set I was referring to above:

https://data.usgs.gov/datacatalog/data/USGS:3a81321b-c153-416f-98b7-cc8e5f0e17c3


By seamless, it means all edges are aligned by Altitude / extent for 'seamless' tiles of coverage (like older 1 Arc-Second.)

Thus, there should be no anomalies within a mile of an airport in the:

USGS 1/3 Arc-Second (~10m) seamless elevation data set.


BTW
: The USGS 1/9 Arc-Second elevation data set you cited above is not yet complete across the CONUS.

GaryGB
 
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us-missouri
I would not limit the max terrain mesh LOD to 12, as FS / P3D SDK Resample will automatically read the optimum output resolution achievable with the supplied source data, and set it to the maximum achievable based on the supplied terrain mesh source data set.

Thus, I would try using LOD=4,Auto.
I will have to re-do the entire United States if I limited everything to LOD 12 in my INF file. Fortunately I can automate a lot of the process and when I'm done apparently things will look even better.
 
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7,443
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us-illinois
Hi Chris:

Some folks (like me) tend to fly "low-and-slow" in areas outide airport test radii, and are thus willing to work with a larger install footprint and content detail rendering burden.

But, if you believe that most flyers that would use your terrain mesh will likely only be at "low-and-slow" altitudes AGL within a mile of airports, you may consider ex-cluding 'higher' LOD resolutions (such as 1/3 Arc-Second) in areas outside FS airport test radii, and thus save on the burden of work updating your product, and any associated download bandwidth expenditure / install footprint size. :idea:

NOTE: FSX / P3D airport test radius may impose a flatten that extends more than a mile outwards to negate terrain detail.


Beware, as well, of the impact that "blended flattens" for airports may have on the ability of FS to display higher LODs near airports: :alert:

https://www.fsdeveloper.com/forum/threads/blending-airports-into-custom-terrain.448048/page-2


Relative to the use of increasingly higher resolution terrain mesh at Levels Of Detail (ex: "LOD" 12) -or larger values:

The FS rendering engine for terrain will always display terrain mesh LODs and texture MIPMAPs as a function of user aircraft distance AGL (either vertical, or the total distance along any tangent to the ground below).

An excellent example of how terrain resolution also 'switches' to lower levels of detail (LODs) as a function of either the hard-coded texture size limits in FS9 versus the greater sizes allowed by FSX and P3D, or as otherwise imposed by FS config file parameter values ...can be seen via the images in Jim Robinson's post here:

https://www.fsdeveloper.com/forum/threads/1024x1024-rock-textures.426477/post-820302


Also to be noted is Jim's animated GIF comparing the terrain in a FS flight location at both LOD-10 and LOD-12 ...here:


After completing a flight over the new mesh I have to say the improvement is pretty lackluster. I paused at a multitude of locations and switched the mesh off and on in the scenery library, took a few screenshots, compared them and yes, there is a slight difference but it's subtle at best. I did a couple comparisons between default LOD10 and the 1/3 arc second/LOD12 mesh in FSX mostly because that's the sim I had running when I decided to do comparisons, here are a couple animated .gifs that show the difference via the "blink comparator" approach:

View attachment 60428

View attachment 60429


Content resolution as a function of user A/C distance is alluded to by Dick Ludowise (aka "rhumbaflappy") via the images in his post here:

https://www.fsdeveloper.com/forum/threads/3-5cm-per-pixel.21121/post-820311

As to what good this does is another question. The radius of the LOD20 wouldn't even extend beyond the nose of a large jet... you would never see it from the cockpit!


Although the cited examples above address the issue of texture MIPMAP display, AFAIK, a comparable mechanism is also operant in the FS terrain subsystem for LOD-related terrain mesh display resolution as a function of user aircraft distance AGL.


Additionally, one may modify FS run time LOD rendering capacity via LOD_RADIUS ...as discussed here:

https://www.fsdeveloper.com/forum/threads/global-mapper-export-question.434552/post-716202


And, of course, FS end users must correct the initially low terrain slider settings imposed by a fresh install of FS as discussed here:

https://www.fsdeveloper.com/forum/t...y-setting-cause-problems-with-terrain.438458/


For a review of QUAD sizes for various LODs used in the FS rendering engine schema, see my composite table of approximate values here:

https://www.fsdeveloper.com/forum/threads/flattens.425495/post-633002

[EDITED]

Note that if one were to use a ~1 meters between elevation data point resolution terrain mesh it would be ~LOD-15, and a ~38.2 meters between elevation data point resolution terrain mesh would be ~LOD-10 in the FS terrain schema (aka 16x less detailed than LOD-15). :pushpin:

[END_EDIT]

GaryGB
 
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490
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us-missouri
Weighing options... looks like I'll just redo all my terrain scenery. Just a matter of how I want the INF files set up. Thanks for all the information Gary!
 
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us-missouri
Are you describing a de-crease of detail in terrain mesh within a mile of the user aircraft on / near ground at an airport ?

If so, this may be due to increased local airport flatten extents.

Or are you instead describing an in-crease of terrain mesh detail within a mile of the user aircraft on / near ground at an airport ?
Regarding your earlier comment about the mesh scenery changing LODs as it enters a certain radius around my aircraft as it flies, I am not changing the source data at all. Just converting the GEOTIF to a BGL. Although this means all my scenery built with LOD=4,12 needs to be replaced, I think maybe my INF setup is at least partly to blame and I am trying your suggestion of LOD=4,Auto and will report back once I've had a chance to test it out.
 
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