[Gvsig_english] raster limitations

[Andre Pais]

Hi there. I´ve downloaded the latest gvSIG version, 1.12 final. I´ve
installed it (activated GRASS and SAGA in the Sextante options) and used
right away because I have an academic work which consists of developing a
spacial analysis exercice using raster operations, first using ArcGIS and
then I must replicate it using an opensource, in my case gvSIG. In the
process, here are a few problems I´ve came up to:

1 - Sextante doesn´t allow to create a DEM-TIN like I did using 3d Analyst
of Arcmap; SAGA has a function called "Shape to TIN" but it doesn´t
generates an output ;

2 - I need to create a DEM in order to generate slope and aspect charts for
my area of study. Since there isn´t an option to define a mask (like there
is in Arcmap), I did a clip using the shape with altimetric information as
input and the area of study as clipping layer. The result has the altimetric
information for my area of study. Then I need to rasterize this result
layer. So I went to Sextante and used "Rasterize vector layer" in order to
convert it to raster format, having defined an appropriate cell size and the
extent as my area of study ( in the hope that the result would have the form
of my area of study). Then I did a void filling ( I´ve read this somewhere)
to generate a proper DEM. But unfortunately the result is a rectangular DEM
instead of being limited to my area of study (which by the way is the
portuguese equivalent to an ayuntamiento) Why?

3 - There is an option in Sextante called "Rasterize vector layer (for
mask)" but it doesn´t seem to do what i want. 


4 - The GRASS function v.to.rast is to confusing and doesn´t work properly.
It gives an error :Failed to import data into GRASS mapset;

5 - The reclassify function of sextante is a bit confusing as well. It
requires a min value, a max value and a new value. For example, if i need to
reclassify a slope chart, e.g, 5 classes (0-10%, 10-20%, 20-30%, 30-40% and
>40%). I have put the min and max for the each class. Why do I need to write
new values? Shouldn´t the program assume that? I´ve tried to write 1, 2, 3,
4 ,5 (to match the classes) but the output has 0 value in some pixels but
there is no class 0. Why?

6 - Why haven´t the programmers of the latest version improved the symbology
options and visualization in rasters. It´s a pain having to work in black,
grey and white and not be able to see the classes of a certain raster with
different colors (with this being shown in the view)


Thank you very much for the attention. I would be really thankful for
answers to my questions. It´s kind of an emergency.

Regards, André Pais. 





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