Simviation Forum - MESH, SRTM, DEM & LOD

May 16^th, 2006 at 9:49pm

Fly2e Offline
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I came across these small definitions and thought I would post them!

MESH is a file which modifies only the relief of a given zone.
A scenery can represent an airport, a city, a building,...
A lanclass modifies the textures applied on the ground.
A afcad modifies the frequencies of airport, radio navigation, the parking's positions, ...

SRTM means Shuttle Radar Topography Mission.
It is one of the mission of the space shuttle, the purpose of which was
to chart the terrestrial relief (90% of emerged world surface).
The data collected at the time of this mission are put has provision of the public.
These data have an accuracy of 90 M (3 seconds of arc),
it is has to say that a point of measurement gives the rise in a square of 90 M with dimensions.
The SRTM are currently the most precise free data.
They make it possible to carry out very great definition meshs, which was impossible
little time ago still.

DEM is the abbreviation for DIGITAL Elevation Model.
the dem files are numerical ground relief representing.
SRTM, GTOPO30 are DEM files.

LOD is the abbreviation of Level Of Detail. The lod is the level of definition that a mesh can represent.
A mesh in lod 9 can reveal details of 76.4 M, in lod 10 it can reveal some of 38.2 M.
while going up of a value of lod, the level of definition is multiplied by 2, the size of the file
increase approximately by 4 (makes some a little less, because of compression).

If the LOD is raised, is the mesh more precise?
No, the mesh precision is only dependent of the the sources precision
Increase the lod will not make the mesh more precise.
the creator use, in general, a lod adapted to the sources precision.
Use a too high lod leads has a loss of FPS.
For the srtm 90 Meters (3 arc seconds), we uses a lod 9, able to represent details of 76.4 M.
The resolution of DEM file is often expressed in arc second.
One arc second corresponds has surroundings 30 M on the equator level .

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Reply #1 - May 17^th, 2006 at 2:45am

FridayChild Offline
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I seriously thought that SRTM meant "Stephen Rothlisberger Terrain Mesh". 8)

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Reply #2 - May 17^th, 2006 at 3:01am

commoner Offline
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Quote:

I seriously thought that SRTM meant "Stephen Rothlisberger Terrain Mesh". 8)

lol...I think as far as FS is concerned THAT is exactlly what it means..........so don't worry FC...we all think the same...........commoner
Wink

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Reply #3 - May 17^th, 2006 at 12:19pm

vololiberista Offline
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This ought to go in the FS2004 faqs at the top of this forum.
Vololiberista

Andiamo in Italia&&

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Reply #4 - May 17^th, 2006 at 12:28pm

cspyro21 Offline
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Quote:

This ought to go in the FS2004 faqs at the top of this forum.
Vololiberista

Indeed - if this topic isn't made a sticky, I back Vololiberista 8)

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Reply #5 - Dec 23^rd, 2010 at 12:41pm

Capt.Propwash Offline
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I know its been covered THOUSANDS of times, but for the sake of the sticky.....

when adding MESH, Landclass, scenery, LOD, STRM data.... in which order from the TOP of the addon menu should things be listed? ie, whats on top of what to get the best detail? or does it really matter???

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Reply #6 - Dec 24^th, 2010 at 1:20am

jgf Offline
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Capt.Propwash wrote on Dec 23^rd, 2010 at 12:41pm:

I know its been covered THOUSANDS of times, but for the sake of the sticky.....

when adding MESH, Landclass, scenery, LOD, STRM data.... in which order from the TOP of the addon menu should things be listed? ie, whats on top of what to get the best detail? or does it really matter???

Mesh is the 3D model of the terrain, so it's the base layer; landclass paints the background (forest, desert, etc.) on the mesh, so it's next; scenery adds the detail (airports, buildings, bridges), it's last. LOD and STRM pertain to the mesh data and have no bearing on scenery layering. On the FS9 scenery page files are ordered from the base at the bottom to the detail at the top, BUT some external scenery managers list the other way around.

Though some people don't agree with this, I put all my mesh files in "...scenery\world\scenery" to reduce the number of items listed (renamed many so they're easy to identify if I need to move them).

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