[GRASS-user] reclass problem

Markus Neteler neteler at osgeo.org
Tue Mar 10 06:34:12 EDT 2009

On Tue, Mar 10, 2009 at 10:59 AM, ambrish dhaka <ambijat at hotmail.com> wrote:
> Hi! all,
> I wish to classify the landuse from the landsat data of 1989. I created a
> 531 (rgb) composite and the features were quite noticeable. The
> relcassification part I tried to use pixel value for creating classes for eg
> 9320 thru 10367 = 1 semiurban etc.
> The problem is that there are other types of areas such as uncultivated
> fields that also get classed into areas such as semiurban. How to deal with
> this.
> And also is there any method to create polygon out of textures. The urban
> areas are quite noticeable by their texture or arrangement of pixel values.
> Is there any floating window formula that can use std dev to create such
> surfaces, I am not sure.

Two quick suggestions:

- mask out zones which aren't of interest (r.mask)
- use a classifier like i.maxlik or better i.smap to perform a statistical
  assignment of pixel values to desired classes.

For an overview, see


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