[GRASS-user] Re: grass-user Digest, Vol 46, Issue 35

[Rich Shepard]

On Fri, 12 Feb 2010, Michael Barton wrote:

> TIN's are a way of creating an elevation surface using vector polygons
> rather than rasters. When computers had slow processors, primitive
> displays, limited RAM, and limited disk space, they were a way of getting
> elevation in a way that optimized hardware limitations. They did so at a
> cost of resolution and simplicity of analysis/processing. They have also
> been used for 2.5D visualization, again to overcome hardware/software
> limitations.

Michael,

   My understanding, which might well be totally incorrect, is that TINs are
better at representing the sloping surface in hilly terrain and, therefore,
provide better hydrological modeling. The differences might very well be
totally insignificant between rainfall-runoff models based on cells and
TINs, except when the basin is a that of a headwater originating stream
reach.

> This is built into the GUI. Bring up a shaded map layer and drape anything
> over any base map.

   OK. I'll give that a try.

> For display outside the GUI there is d.shaded.map  -- which is a script
> that calls d.his to do this.

   Good to know. Thanks.

Rich