## "Iso"-Lines

### "Iso"-Lines

Hi!
I am looking for an Algorithm, which is capable to generate "iso"-Lines
out of a set of points. That means:
I have a number of Points, e.g. X/Y and pressure. In this case i want to
generate isobares (is this the correct term). I tried to interpret pressure
as z-value and generated triangles. Then i computete the intersection between
a Plane of constant z and the triangles. The Result: Lines of equal pressure.
But: The lines are ugly because they consist of straight segments. For a
map-like plot i need smooth curves. I tried splines, but there are cases, when
those splines intersect. Any solution out there?
Ciao, Udo

## CrossPoint v2.1 ##

### "Iso"-Lines

|> I am looking for an Algorithm, which is capable to generate "iso"-Lines
|> out of a set of points. That means:
|> I have a number of Points, e.g. X/Y and pressure. In this case i want to
|> generate isobares (is this the correct term). I tried to interpret pressure
|> as z-value and generated triangles. Then i computete the intersection between
|> a Plane of constant z and the triangles. The Result: Lines of equal pressure.
|> But: The lines are ugly because they consist of straight segments. For a
|> map-like plot i need smooth curves. I tried splines, but there are cases, when
|> those splines intersect. Any solution out there?
|> Ciao, Udo

You will find some answers in my book -

CONTOURING: A guide to the analysis and display of spatial data,
Pergamon Press, 1992, ISBN 0 08 040286 0

This book catalogues and categorizes all the published methods I could
find and has about 600 references.  The code that comes with the book
implements 18 interpolation methods, 5 gradient estimation methods, and
7 display methods.  Apparently the most useful, reliable, and general,
method is natural neighbour interpolation.  This is a relatively unknown
weighted average method using a variable number of area-based local
coordinates.

Details of a commercial gridding program using natural neighbour
interpolation is available by email from the undersigned.
--

Department of Mathematics                         Tel: (61 9) 380 3359
The University of Western Australia               FAX: (61 9) 380 1028
Nedlands, WA 6009  Australia.          Real data are full of surprises

### "Iso"-Lines

Hi!
I am looking for an Algorithm, which is capable to generate "iso"-Lines
out of a set of points. That means:
I have a number of Points, e.g. X/Y and pressure. In this case i want to
generate isobares (is this the correct term). I tried to interpret pressure
as z-value and generated triangles. Then i computete the intersection between
a Plane of constant z and the triangles. The Result: Lines of equal pressure.
But: The lines are ugly because they consist of straight segments. For a
map-like plot i need smooth curves. I tried splines, but there are cases, when
those splines intersect. Any solution out there?
Ciao, Udo

## CrossPoint v2.1 ##

### "Iso"-Lines

> Hi!
> I am looking for an Algorithm, which is capable to generate "iso"-Lines
> out of a set of points. That means:
> I have a number of Points, e.g. X/Y and pressure. In this case i want to
> generate isobares (is this the correct term). I tried to interpret pressure
> as z-value and generated triangles. Then i computete the intersection between
> a Plane of constant z and the triangles. The Result: Lines of equal pressure.
> But: The lines are ugly because they consist of straight segments. For a
> map-like plot i need smooth curves. I tried splines, but there are cases, when
> those splines intersect. Any solution out there?

Try Algorithm 626 from netlib. Login to
ftp.zib-berlin.de
goto pub/netlib/toms
get 626

send 626 from toms

This is an algorithm in Fortran that interpolates
with quintics and avoids intersections.

Sincerely
A.Preusser

Does anyone have a problem using PhotoShop 3.  I have alien skin filters
and Kai's Power Tools and yet if I use the spheroid designer in Kai's Power
Tools and then try to add a drop shadow to it using alien skin, PhotoShop
crashes.  Has anyone got a solution to this problem.  It's really bugging
me (pun not intentional).

Yours Pete