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Message: 3
Date: Tue, 28 Aug 2012 10:45:22 +0200
From: Paolo Cavallini<[email protected]>
To:[email protected]
Subject: Re: [Qgis-user] 0, null values and color table GRASS/QGIS
Message-ID:<[email protected]>
Content-Type: text/plain; charset=ISO-8859-1
Il 28/08/2012 09:24, Patrick Giraudoux ha scritto:
Hi,
I am using QGIS 1.7.0 Wroclaw (and GRASS 6.4.1 inside).
This is old, please upgrade to 1.8.
Thanks.
-- Paolo Cavallini - Faunalia www.faunalia.eu Full contact details at
www.faunalia.eu/pc Nuovi corsi QGIS e PostGIS:
http://www.faunalia.it/calendario
Absolutely, right. It works OK in 1.8.0-Lisboa. Thanks.
Patrick
Le 28/08/2012 09:24, Patrick Giraudoux a écrit :
Hi,
I am using QGIS 1.7.0 Wroclaw (and GRASS 6.4.1 inside).
I have some troubles with map displays in QGIS with 0 and null values.
I just want to extract a particular habitat category from a Global
Land Cover 2000 raster into a raster of presence/absence (and NULL
value for ocean and waterbodies)
This makes the following:
r.mapcalc "V7_01=if(AsiaGLC2000==7,1,0)"
So far so good, I get a raster V7_01 with null values and 1 for pixel
of category 7, 0 for the others and null values stay NULL. All is
correctly displayed by QGIS.
Now, I would like to transform V7_01 into a floating point map, and
then use r. neighbors for a neigborhood analysis.
r.mapcalc "V7=1.0*V7_01"
I get a raster named V7 BUT strangely for any color table, 0 value is
considered NULL (transparent) when displayed by QGIS. However, the
original NULL values are well kept and distinct in this raster (e.g.
NULL pixels are informed as NULL and 0 pixels are 0, respectively,
which is correctly displayed within GRASS).
An indication about what happen is that the metadata inform that null
values(nodata) are -2.14748e+09 in AsiaGLC2000 and V7_01, but become
2.22507e-308 in V7 (so close to 0).
Any suggestion welcome, I am stuck...
Patrick
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