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

[Jed]

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. 
> 

I'm curious why you say TINs are used at the "cost of resolution"? What if I
have a surface sampled by a dense irregularly spaced point data set, e.g. a
lidar point cloud. If I create a TIN using a delaunay triangulation of those
points the resulting model will exactly pass through all of the original
data points with linear interpolations between. As a result it resolves all
of the detail in the original data. In contrast, if I use a raster map to
model the surface it will inevitably lead to some degree of aggregation as a
function of the interpolation method I choose. The same is true if I want to
incorporate linear features such as breaklines into the model. Of course,
the question of which type of model is more useful for a given application
is entirely separate.

Best,

-- 
Jed Frechette

University of New Mexico Lidar Lab
www.unm.edu/~lidar
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