I suggested the -where option because your shapefile had only two features that are (almost)inverse of each other. You can select only one of them. You might want to use the -at option with this.
What do you mean by 'most representative value'? On Fri, Aug 5, 2011 at 5:40 PM, Etienne <[email protected]> wrote: > Hi and thanks! > > I set the init value to 255, and the overlapping pixels are set to that > value (instead of the default of 0). > > Unfortunately, using -where resulted in the same gaps not being filled, and > a combination of -where and -at selects too many pixels (the borders all > overlap). > > Looking more closely, it seems that the problem is almost exclusively where > there are tiny gaps between the polygons. > > It seems that -at doesn't leave any gaps, although it favors the > higher-index values (as they are processed later, presumably). > I would prefer to have the most representative value, any hints? > > many thanks, Etienne > > ------------------------------ > *From:* Chaitanya kumar CH <[email protected]> > *To:* Etienne <[email protected]> > *Cc:* "[email protected]" <[email protected]> > *Sent:* Friday, August 5, 2011 4:22:10 AM > *Subject:* Re: [gdal-dev] problem rasterizing categorical data from > shapefile - 0 values at some intersections > > Etienne, > > Rasters of type Byte cannot hold values below 0. So, the nodata value of -1 > is not practical. It's better to choose 0 or 255 depending on your data or > choose a different data type. > > Your problem arises because the two geometries in the shapefile overlap in > some places and leave some gaps between them in other places. > Consider selecting only one feature using the -where option in > gdal_rasterize. You can also use the -at option but it may not work at all > resolutions. > > On Fri, Aug 5, 2011 at 7:40 AM, Etienne <[email protected]> wrote: > > Hi all, > > I am trying to create a raster file with categorical data (land > vegetation/cover positive indices) from a shapefile containing 1 layer of > polygons. > > I use the following command: > gdal_rasterize -tr 0.0005 0.0005 -a_nodata -1 -of GTiff -a_srs EPSG:4618 > -a "CLASSE_ID" -ot Byte -init -1 -l region1 region1.shp region1-3.tif > > This creates a map which looks good, but there are some holes in the data, > (individual pixels with a value of 0) at the intersection of 2 polygons. It > looks like the > intersections pass through the exact center of these pixels. These pixels > are not set to missing(-1). Depending on the output resolution, different > pixels get set to a value of 0. > > Has anyone ran into this problem? Any idea how to fix this? > Those interested will find 2 small shapefiles here: http://db.tt/3X4hI45and > http://db.tt/phqnGci > > > I tried using gdal_grid, but it doesn't seem to support a shapefile with > POLYGONs. > > many thanks! > Etienne > > _______________________________________________ > gdal-dev mailing list > [email protected] > http://lists.osgeo.org/mailman/listinfo/gdal-dev > > > > > -- > Best regards, > Chaitanya kumar CH. > > +91-9494447584 > 17.2416N 80.1426E > > > -- Best regards, Chaitanya kumar CH. +91-9494447584 17.2416N 80.1426E
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