[Gvsig_english] raster limitations

[maria maluenda]

On 26/09/12 16:25, Andre Pais wrote:
> 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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Hi, you could have a look at videos [1] and [2]. They belong to previous 
versions but could be useful.

[1] http://www.youtube.com/watch?v=T0-_ny4Cj9U
[2] http://www.youtube.com/watch?v=IY0HlHLadwU

Regards

-- 
María Maluenda Rico
Proyecto gvSIG
Conselleria d'Infraestructures, Territori i Medi Ambient
València (Spain)

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