[GRASS-user] Which NASA Blue Marble datasets should I used to create a DEM with texture mapping?

[Hamish]

Elvis Dowson wrote:
> I have a very basic question. I want to create a DEM of a  
> particular region. The DEM is a height field representation, in a
> raster image format. I can directly generate elevation data
> using this information. Looking at the NASA Blue Marble dataset,
> you have a topographic file that represents the topographic data.

NASA's Blue Marble is a visual representation of the Earth (sans clouds),
not a topographic one. There is no elevation associated with it besides
shading.

> Now, after I use the topographic data to reconstruct the 3D surface, I  
> need to texture map the 3D terrain with image data. For this I guess I  
> could use the normal NASA Blue Marble images without topograhic or  
> bathymetric data.

For a single SRTM tile, r.in.onearth LANDSAT may be a much smaller
download than the Blue Marble data.  (wiki addons)

 
> Question 01: What is the use of the NASA Blue Marble images with both  
> topographic and bathymetric data? Is it useful for creating a DEM with
> textured data?

it is nice to look at.. more natural to navigate by.. shrug

e.g. you can drape the Blue Marble image over the SRTM (ETOPO) topography
with nviz (after r.composite to merge R,G,B layers of Blue Marble):

nviz elev=srtm color=bluemarble.composite

http://grass.osgeo.org/wiki/Blue_Marble#Processing

> Question 02: How does NASA's SRTM v2.0 data fit into all this? SRTM if
> I understand correctly is DEM data.

yes, it is elevation.

> Is SRTM and the NASA Blue Marble data set connected in some way?

just that they cover the earth and both paid for by the US.


Hamish