Terrain mesh introduction

[jtanabodee]

Mesh

Discussion thread for Mesh. If you would like to add a comment, click the Post Reply button.

 

[Timmo]

DTM (Digital Terrain Model) - The 'bald' earth model. Vegetation, buildings, and other cultural features digitally removed, leaving just the underlying terrain.
DEM (Digital Elevation Model), aka DSM (Digital Surface Model) - Includes buildings, vegetation, and roads, as well as natural terrain features.

This is stated in the Wiki- I disagree.

DTM and DEM are simply different names for the same thing and are used interchangeably. The names dont relate to whether 'non ground' and 'ground' features are included in the terrain model.

I do agree it may be useful to make the distinction between DEMs/ DTMs that include houses/trees etc, especially now that FSX has the ability to display high resolution terrain.

For the most part, this is only an issue with high resolution terrain data gathered by LiDaR. Users sourcing this data may need to ask for the 'Ground' DTM for use in FS

 

[=Hollywood=]

Actually DEM can be both DTM and DSM...

DEM = Digital Elevation Model

DTM = Digital Terrain Model (i.e. bald earth)
DSM = Digital Surface Model (i.e. first return lidar/ifsar/other synthetic aperture radar technology)

DEM is more all encompasing, and these days is more tied to the old USGS "DEM" format and seems to be a dying entity in terms of GIS language... With so many new sources of elevation data the original meaning has been further clarified by the introduction of the DTM/DSM designations...

And yes, FS definitely needs DTM data ;-) Unless users have a way to pull away buildings and vegetation height maps from the model..

 

[BASys]

Hi Folks

EDIT -
I'd created this post, and revised the wiki, at 07:40, but forgot to click submit.
Danged multiple windows.

Timmo -
Revised as -

DEM (Digital Elevation Model/Map), available in two main types -

* DTM (Digital Terrain Model) - The 'bald earth' model. Vegetation, buildings, and other cultural features removed, leaving just the underlying terrain.
* DSM (Digital Surface Model) - The 'canopy' model. Includes buildings, vegetation, and roads, as well as natural terrain features.

Mean't to address these previously,
need rewording for clarity -

All scenery objects are placed in relation to the mesh

Scenery objects are placed either -
- relative to terrain (AGL), e.g. Buildings
- relative to mean sea-level (MSL), e.g. ANOs - masts & chimmneys, etc.

As mesh & terrain elevation aren't nescessarily the same,
i.e. on airports, or other applied flattens.

Maybe use 'terrain', rather than 'mesh' ?

With the release of FSX, a fully three dimensional mesh was introduced

Use 'earth model', rather than 'mesh'.
Mesh has always been 3D.



HTH
ATB
Paul

 

[arno]

Maybe use 'terrain', rather than 'mesh' ?

Agreed. Although mesh scenery is still a term used often for this kind of scenery it is confusing. We'd better call it terrain (that is also the new I gave to that category on the Wiki).

Use 'earth model', rather than 'mesh'.
Mesh has always been 3D.

I am wondering what is new about the terrain in FSX, especially with regard to the 3D part. I don't think there has been a big change compared to FS2004.

 

[Timmo]

I am wondering what is new about the terrain in FSX, especially with regard to the 3D part. I don't think there has been a big change compared to FS2004

Yep, I think I wrote that part...What I was trying to say is that in FS2004, 'flat areas' (I.e. the ocean) were indeed flat- an infinite plane onto which 'terrain' was added. In FSX, 'flat areas' are in fact curved around the surface of the globe. There is a good paper on the FSX modified RQT mesh system buried on Fsinsider somewhere.

That is also what I mean for 'full 3D mesh' but I agree, it could be worded better (full 3D could also be interpreted to mean that tunnels and overhangs were possible using FS terrain)....I wonder how TS gets around this? Do users just travel 'through' the terrain in a 3D model of a tunnel?

Also, agree about using the word 'terrain' as opposed to mesh.

 

[arno]

OK, understand it now. I guess we might better say that the curvation of the earth is now taken into account correctly. I think that is what you want to say .