[GRASS-user] Land-use mapping troubles

[Sitansu pattnaik]

Please email to the group so that you get additional responses.

I do not think you need to group the rasterized training data with the
Landsat image group. Use i.group to define the group and the subgroup.
You need to also check how many pixels are within each training polygon. If
you have only chosen a few points, i.maxlik will not generate
any usable results.

http://grass.osgeo.org/grass64/manuals/i.group.html

Please share the actual commands which were used in the entire process.

Sitansu @ kCube

On Tue, Mar 19, 2013 at 4:55 PM, Devica Ranade <devicaranade at gmail.com>wrote:

> Hello,
>
> Thanks a lot for the reply!
> I can see the imported bands clearly within GRASS. They were LANDSAT
> images in tiff format.
> I created a polygon vector file using my ground-truthing data points in
> QGIS and converted it into a raster (tiff format) . I further imported this
> raster into GRASS and tried doing supervised classification using a group
> (my group included the newly made raster map and my original LANDSAT image
> that I wanted to be classified) and subgroup.
> On running Maximum Likelihood Classification, I got the result I have
> attached in the previous email!
>
> I have tried this quite a few times now, only to get the same map.
>
> Any help will be really appreciated!
> Thanks a lot again,
> Devica..
>
>
>
> On Tue, Mar 19, 2013 at 3:42 PM, Sitansu pattnaik <sitansu at gmail.com>wrote:
>
>> At first glance, it looks like there is a problem with data import. If
>> you are able to see the imported bands clearly within GRASS, then there
>> could be problems with the signature collection process. Your current
>> output looks like the row numbers have been classified instead of the data
>> values stored in each pixel.
>> If you can share more information about the data source including format
>> and the steps you have taken for classification ( groups and subgroup
>> definiton ), someone can troubleshoot your problem.
>>
>> Sitansu @ kCube
>>
>> On Tue, Mar 19, 2013 at 3:22 PM, Devica Ranade <devicaranade at gmail.com>wrote:
>>
>>> I have been trying to do some land use mapping using GRASS.
>>> While doing a supervised classification for my LANDSAT image, I got a
>>> very weird map shown below. (screenshot also attached with this email.)
>>>
>>>
>>>
>>> Can I please know if this problem is common and if yes, what is the best
>>> way of dealing with it?
>>>
>>> Thanks a lot,
>>>
>>> Devica..
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>>>
>>>
>>
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>
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