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 .
"In theory, there is no difference between theory and practice. But, in practice, there is."
