[GRASS-user] i.maxlik can't read signature from i.class

[Cesar Augusto Ramírez Franco]

Hello Venka

Thank you for your response

Unfortunately, I did rescale my lsat8 images to 8bit, however, I tested
with North Carolina sample dataset which is Landsat 7 (8bit) and got the
same error, so it must be something else, maybe i.class generating a wrong
signature file?


2013/11/26 Venkatesh Raghavan <raghavan at media.osaka-cu.ac.jp>

>  Hi Augusto,
>
>
> In GRASS-6.4.3, i.class only works on 8bit images. Since the Landsat 8
> products are
> 12bit data, proper signature files cannot be produced by i.class.
>
> You could try rescaling data to 8bit and see if i.class and i.maxlik works.
>
> Best
>
> Venka
>
> P.S. I hope i.class will be support 12, 16bit images in future.
>
>
>
> On 2013/11/27 0:47, Cesar Augusto Ramírez Franco wrote:
>
> Hello everyone,
>
> I've been trying to do a supervised classification from landsat8 imagery
> using i.class and then i.maxlik, but I'm getting an error when running
> i.maxlik saying it can't read the signature file.
>
> I tested my procedure on the NC sample dataset and I'm getting the same
> error, I'm using Grass 6.4.2 on Debian Wheezy, installed from the debian
> repo. Here's the command set:
>
> #Display RGB enhanced map
> i.landsat.rgb blue=lsat7_2000_10 green=lsat7_2000_20 red=lsat7_2000_30
> d.rgb blue=lsat7_2000_10 green=lsat7_2000_20 red=lsat7_2000_30
> #"Real color" map
> r.composite red=lsat7_2000_30 green=lsat7_2000_20 blue=lsat7_2000_10
> output=lsat7_2000_RGB
> #Group images to process
> i.group group=lsat7_2000_RGB subgroup=lsat7_2000_RGB
> input=lsat7_2000_10,lsat7_2000_20,lsat7_2000_30
> #Unsupervised classification
> i.cluster group=lsat7_2000_RGB subgroup=lsat7_2000_RGB sigfile=clustlsat7
> classes=20 report=rep_clust_lsat7.txt
> i.maxlik group=lsat7_2000_RGB subgroup=lsat7_2000_RGB sigfile=clustlsat7
>  class=lsat7_classes reject=lsat7_classes_rej
> #Supervised classification
> i.class map=lsat7_2000_RGB group=lsat7_2000_RGB subgroup=lsat7_2000_RGB
> outsig=classlsat7
> i.maxlik group=lsat7_2000_RGB subgroup=lsat7_2000_RGB sigfile=classlsat7
> class=lsat7_class_sup
>
> Here I get the error in which i.maxlik can't read the signature file
> created by i.class (classlsat7) but read the one created by i.cluster
> flawlessly
>
> This is what I'm selecting on the i.class monitor, I named it vegetation:
> [image: Imagen integrada 1]
>
> And the contents of the classlsat7 signature file are the following:
>
>
>  ​
>
>
>  #
>
> #vegetation
>
> 166
>
> ​
>
>   Am I doing something wrong or is it some kind of bug?
>
>
>
>
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-- 
*César Augusto Ramírez Franco*
Laboratorio de Sistemas Complejos Naturales
Escuela de Geociencias
Facultad de Ciencias
Universidad Nacional de Colombia - Sede Medellín
Teléfono: (57-4) 430 9369 - 301 389 5607
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