Hello!
Although your message is already some days old I wanna respond.
Did you ever want gdal_contour to produce polygons instead of lines?
Yes!
I made a small Perl program that uses the Perl bindings to GDAL and
which converts the lines into polygons. The polygons represent "plates"
of equal elevation and thus overlap. The polygons are stored into a new
layer in such an order that ordered rendering of them produces a nice
visualization. Visualization is my main goal here - I want to get a
similar effect as in some weather forecasts. However, transparency does
not work as expected in standard viewers because of overlapping
polygons. Here's an example created from DEM:
http://map.hut.fi/files/misc/contour_polygons.png
The code is also at http://map.hut.fi/files/misc/
I found this by googling:
http://lists.maptools.org/pipermail/fwtools/2005-November/000199.html
I wonder what's the current situation. Does GRASS do this?
It seems that GRASS cannot do this in a satisfying way. Or at least it
appears to be (don't wanna offend any GRASS dev/user).
Here I asked fro something similar:
http://thread.gmane.org/gmane.comp.gis.grass.user/24889
The maps I created with the suggested approach looked exactly as your
screenshots. The converted vectors didn't follow the countourlines
smouthly. Instead, the borders retraind the pixel-like raster outline.
Matplotlib and other plotting programs (matlab, IDL) can do this (see
the examples here: ).
So either
* plotting programs do an inaccurate interpolation
or
* the GRASS approach is too complicated that even experience users don't
find it.
Kind regards,
Timmie
_______________________________________________
gdal-dev mailing list
[email protected]
http://lists.osgeo.org/mailman/listinfo/gdal-dev
