# Creating simplified (binned) polygons from raster file?

I have esri ascii grid raster files like

``````ncols 4
nrows 3
xllcorner 0
yllcorner 0
cellsize 1
nodata_value -999
1 2 3 4
4 21 3 3
3 2 31 1
``````

How can I convert this into vectorized (WKT) format when simplifying / reducing polygons via a binning of the values i.e. neighbors within a range of 0...10...20...30 should be put into the same polygon.

Naively this translates to

``````1.0;POLYGON ((1 3, 0 3, 0 2, 1 2, 1 3))
4.0;POLYGON ((1 1, 1 2, 0 2, 0 1, 1 1))
3.0;POLYGON ((0 1, 0 0, 1 0, 1 1, 0 1))
2.0;POLYGON ((1 2, 2 2, 2 3, 1 3, 1 2))
21.0;POLYGON ((1 1, 2 1, 2 2, 1 2, 1 1))
2.0;POLYGON ((1 1, 1 0, 2 0, 2 1, 1 1))
3.0;POLYGON ((3 1, 4 1, 4 2, 3 2, 3 3, 2 3, 2 1, 3 1))
31.0;POLYGON ((3 1, 2 1, 2 0, 3 0, 3 1))
4.0;POLYGON ((3 2, 4 2, 4 3, 3 3, 3 2))
1.0;POLYGON ((4 0, 4 1, 3 1, 3 0, 4 0))
``````

I can aggregate/bin the numbers into a range from 0...100 with steps of 10 and group-by aggregate (ST_CONCAT/ST_UNION) the geometries, but this is not what I want to achieve. I.e. When creating the polygons I would rather only want to create them in aggregated fashion. So for the value range, it should be already in the binned range, and for the polygons they should be considered neighbors if a) next to each other b) binning interval is the same.

• What GIS software are you using? What have you tried?
– PolyGeo
Jun 2 '17 at 12:24
• open source: gdal, geotools, ogr Currently I tried to use `ST_UNION` like concatenation of the polygons into multiploygons but this is not what I am after. I want to have separate polygons but fewer of them. I am looking for something similar to postgis.net/docs/manual-2.2/ST_Simplify.html i.e. currently I am binning only the values, but during the process of poligonize-everything I would also like to reduce the polygon count and get fewer but bigger polygons Jun 2 '17 at 12:25
• I read that geotools is providing DouglasPeuckerSimplifier and TopologyPreservingSimplifier which will simplify a single Geometry, I would rather want to simplify across geometries have a smaller number of polygons. Jun 2 '17 at 13:15