Thanks for the answer Antonio. Unfortunately I didn´t quite well understand your answer to question 5. My slope classes are: 0 - 10; 10 - 20; 20 - 30; 30 - 40 e >40 so i would do this:<div><br></div><div>min value max value new value</div>
<div> 0 10 1 Sextante - Reclassify - Min < x <= Max</div><div> 10 20 2</div>
<div> 20 30 3</div><div> 30 40 4</div><div> 40 101.25 (my max slope) 5</div>
<div><br></div><div>By the way is it normal to have a max slope over 100%? I used a DEM created in Arcmap and converted it to TIF so that I could use it in gvSIG since I didn´t know how to use a mask in gvSIG (now I know thanks to you). Then I went to Sextante > Slope > Percentage, Travis et al. 1975.....the result varies from 0 to 101.25.</div>
<div>Thanks for the attention once again.</div><div><br><div class="gmail_quote">2012/9/27 Antonio Falciano [via OSGeo.org] <span dir="ltr"><<a href="/user/SendEmail.jtp?type=node&node=5004919&i=0" target="_top" rel="nofollow" link="external">[hidden email]</a>></span><br>
<blockquote style='border-left:2px solid #CCCCCC;padding:0 1em' class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div class="im">
Il 26/09/2012 16.25, Andre Pais ha scritto:
<br></div><div class="im">> Hi there. I´ve downloaded the latest gvSIG version, 1.12 final. I´ve
<br>> installed it (activated GRASS and SAGA in the Sextante options) and used
<br>> right away because I have an academic work which consists of developing a
<br>> spacial analysis exercice using raster operations, first using ArcGIS and
<br>> then I must replicate it using an opensource, in my case gvSIG. In the
<br>> process, here are a few problems I´ve came up to:
<br><br></div>Hi Andre,
<br><div class="im"><br>> 1 - Sextante doesn´t allow to create a DEM-TIN like I did using 3d Analyst
<br>> of Arcmap; SAGA has a function called "Shape to TIN" but it doesn´t
<br>> generates an output ;
<br><br></div><div class="im">The first one is a known limitation of gvSIG and SEXTANTE, because they
<br>are not able to manage a 3D TIN at the moment, but this is not the only
<br>way to create DEM fortunately.
<br>The second one may depend by SAGA (and GRASS) bindings in SEXTANTE which
<br>are not stable yet and so not all SAGA modules work fine.
<br></div><div class="im"><div><div class='shrinkable-quote'><br>> 2 - I need to create a DEM in order to generate slope and aspect charts for
<br>> my area of study. Since there isn´t an option to define a mask (like there
<br>> is in Arcmap), I did a clip using the shape with altimetric information as
<br>> input and the area of study as clipping layer. The result has the altimetric
<br>> information for my area of study. Then I need to rasterize this result
<br>> layer. So I went to Sextante and used "Rasterize vector layer" in order to
<br>> convert it to raster format, having defined an appropriate cell size and the
<br>> extent as my area of study ( in the hope that the result would have the form
<br>> of my area of study). Then I did a void filling ( I´ve read this somewhere)
<br>> to generate a proper DEM. But unfortunately the result is a rectangular DEM
<br>> instead of being limited to my area of study (which by the way is the
<br>> portuguese equivalent to an ayuntamiento) Why?
</div></div></div><div class="im">This behavior is what we should expect. In fact, the result of Void
<br>filling doesn't take in count your mask because of its definition: it
<br>"completes the information of one raster layer that has cells without
<br>data. The information to complete the cells without data is taken from
<br>the surrounding cells using interpolation methods." (Source: SEXTANTE
<br>help). So the mask should be applied after (and not before) the Void
<br>filling by multiplying them.
<br><br></div><div class="im">> 3 - There is an option in Sextante called "Rasterize vector layer (for
<br>> mask)" but it doesn´t seem to do what i want.
<br><br></div><div class="im">I have tried it and seems to work like a charm. Its result should be a
<br>mask with ones where there are vector geometries, otherwise zero.
<br><br></div><div class="im">> 4 - The GRASS function v.to.rast is to confusing and doesn´t work properly.
<br>> It gives an error :Failed to import data into GRASS mapset;
<br><br></div><div class="im">See my answer to the point 1. These are SEXTANTE bugs, I'm sorry.
<br><br></div><div class="im">> 5 - The reclassify function of sextante is a bit confusing as well. It
<br>> requires a min value, a max value and a new value. For example, if i need to
<br>> reclassify a slope chart, e.g, 5 classes (0-10%, 10-20%, 20-30%, 30-40% and
<br>>> 40%). I have put the min and max for the each class. Why do I need to write
<br>> new values? Shouldn´t the program assume that? I´ve tried to write 1, 2, 3,
<br>> 4 ,5 (to match the classes) but the output has 0 value in some pixels but
<br>> there is no class 0. Why?
<br><br></div><div class="im">Because it's not possible to write in the reclassified raster "0-10%",
<br>"10-20%", "20-30%", "30-40%" and "> 40%", so let's say we need some
<br>aliases in order to do this task. AFAIK it works everywhere in this way.
<br><br></div><div class="im">> 6 - Why haven´t the programmers of the latest version improved the symbology
<br>> options and visualization in rasters. It´s a pain having to work in black,
<br>> grey and white and not be able to see the classes of a certain raster with
<br>> different colors (with this being shown in the view)
<br><br></div><div class="im">You can apply the color table you like, as Francisco suggested.
<br><br>Cheers,
<br>Antonio
<br><br>--
<br>Antonio Falciano
<br><a href="http://www.linkedin.com/in/antoniofalciano" rel="nofollow" link="external" target="_blank">http://www.linkedin.com/in/antoniofalciano</a><br>_______________________________________________
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