Importing Elevation data from an ASCII format

[Darrell McCauley]

Brian Culpepper (brian at cast.uark.edu) writes on 9 Dec 93:
>Tom Nelson writes:> 
>> 
>> with a sites file then do either s.surf.idw or s.surf.tps.
>> Both create a surface file but tps takes a lot longer and with possibly better results.

>I will have to disagree with "do either s.surf.idw or s.surf.tps". These two
>interpolation modules are NOT the same! If you are creating an elevation surface

The important thing here is the underlying model that the data should
follow, characteristics of the program (smoothing or exact), and the
quality of the output.

IDW will tend to give peaks at the point values, which may not be
desirable.  Exact interpolators (e.g., s.bissf, an implmentation of
Akima's method, forthcoming) expects data with no noise
(bissf=Bivariate Interpolation and Smooth Surface Fitting). TPS can do
smoothing, which is good for most of the kind of data that I've seen
grass folks working with.

The original poster may also be looking for s.to.rast, a contrib
program, that does not do any interpolation but simply makes each
site into a cell (depending on your resolution, see 'g.region -p').

--Darrell