Hello Andrea,
I have been doing similar work with GRASS. My data was taken
from a coastline in the form of x,y and z. The data was
imported using s.in.asci and to make the map I used
s.surf.tps. I found that it gave me a better approximation
of the coast.
When you look at the map you produced did it look like blocks
and not a smooth line? If so, I had the same problem and
used a inhouse program to convert to a uniform grid. This
seemed to solve the problem. s.surf.tps will then make
a nice raster map for you.
If anyone has a better solution for irregular spaced data,
it would be welcomed.
Hope this helped.
Kym M. Lenkus
Davidson Laboratory
KLENKUS1@VAXC.STEVENS-TECH.EDU (KLENKUS1@VAXC.STEVENS-TECH.EDU) writes on 21 Jan 94:
I have been doing similar work with GRASS. My data was taken
from a coastline in the form of x,y and z. The data was
imported using s.in.asci and to make the map I used
s.surf.tps. I found that it gave me a better approximation
of the coast.
If anyone has a better solution for irregular spaced data,
it would be welcomed.
Maybe not "better," but "alternative" solutions are being developed
(see appended). TOMS 677 can supposedly deal well with data that
have steep slopes (like your coastline problem).
See the article in ACM Trans. on Math. Soft. (TOMS).
--Darrell
I am currently working on the following for my own purposes:
s.bissf ACM Trans. on Math. Soft. Algorithm 677
(Akima's method)
s.masub ACM Trans. on Math. Soft. Algorithm 677
s.c2grid ACM Trans. on Math. Soft. Algorithm 684
s.qshep2 ACM Trans. on Math. Soft. Algorithm 660
(Modified Shepard's Method)
(which offer alternatives to s.surf.idw and s.surf.tps).
These are currently being developed and may be contributed
to GRASS if I can get them working.