interpolation programs

[Dave Gerdes]

> Date: Thu, 16 Jul 92 13:31:59 EST
> From: simon at cerberus.earth.monash.edu.au (Simon Cox)
> Message-Id: <9207160331.AA02871 at cerberus.earth.monash.edu.au>
> Sender: lists-owner at amber.cecer.army.mil
> Reply-To: grassu-list at amber.cecer.army.mil
> Precedence: Bulk
> To: grassu-list at amber.cecer.army.mil
> Subject: interpolation programs
> 
> 
> 
> 
> Are there any interpolation programs for grass out there EXCEPT 
> the idw pair?  
> 
> Inverse distance weighting may be fast and easy, but 
> it does not produce very good results for some types of problem - 
> 
> eg if you have a "surface" which you *know* is smoothly varying, 
> (eg geophysical data)
> then some form of surface fitting (polynomial, spline, etc) can be 
> better - it allows you to find peaks between the data points, whereas the 
> idw algorithm will NEVER produce a value higher (or lower) than 
> the surrounding values.
> 
> Thanks for your assistance
> 
> Simon Cox
> Dept of Earth Sciences
> Monash University
> Clayton,  Vic  3168   Australia
> 


We have a program which uses thin plate splines.  I have been meaning to 
put it out for distribution but everytime I think I will, the programmers
come up with another major enhancement.  I will try to get it out
this week for you.  It is called  s.surf.tps.   It uses site
file data.  I will include the source for a program which will dump
out every point from a labeled vector file as site info.  With that, you
can convert contour data to site to be used as input.

-- 



  Dave Gerdes
  US Army Construction Engineering Research Lab
  Spatial Analysis & Systems Team
  dpgerdes at cerl.cecer.army.mil
  (217) 352-6511 x591