[GRASS-user] Signature made by i.class not accessible?

[Nikos Alexandris]

On Mon, 2008-03-03 at 13:40 +0200, Paula.Sankelo at fimr.fi wrote:
> Hello all,

Hi!
> 
> I'm a very new GRASS user,

me as well ;-)

>  and I hope this matter hasn't been discussed many times before. (And
> I hope this message doesn't arrive to you many times: I've tried
> sending it two times so far, and with no success. Now I'm trying from
> my work address, let's see if this helps.)
> 
> I'm using GRASS 6.3 and I'm having some trouble with the i.class
> module. I've learned to go around the first problem, but not the other
> one, and it has halted my work now.
> 
> The first problem arises if I try to start i.class by just typing
> "i.class" into the command line. I am queried for the raster map I
> want to obtain the signatures from, and then the image group, and so
> far all is well. But when I'm queried for the image subgroup, the
> subgroup I give is never OK, and if I type "list" for the available
> subgroups, there never seem to be any subgroups in my image group. I
> have created the appropriate image groups and subgroups using i.group,
> and have used them succesfully with other
> applications, so the subgroup should be there. However, the i.class
> doesn't see it, at least not when I start it that way.
> 
> I can go around this problem, if I specify the group and subgroup
> already when calling i.class, i.e. if I type
> 
> i.class map="name" group="name" subgroup="name" outsig="name"
> 
> Then the graphic window opens up nicely and I can specify the training
> regions. But then another trouble comes along.
> 
> After I've selected and saved and named all my training regions, and
> exited i.class, all seems to be OK, and signature file is saved. But
> when I start i.maxlik and try to use the created signature file for
> classifying, I get the error message:
> 
> ERROR: Can't read signature file [signature].

Not sure if I can help. Just some ideas:

1. You enter always the same LOCATION in which you created the
signatures?
2. Read/Write/Execute permissions for your GIS-DB ok?
3.Subgroup needs more than 1 raster map to work with i.maxlik
> 
> When I run i.maxlik with a signature file created by i.cluster, I
> don't have any problems. Why can't I open the signature I've created
> with i.class? I can see the signature file listed under /subgroup/sig/
> so it has been created, it just can't be accessed by i.maxlik. I've
> tried again and again, I've tried saving the signature with different
> names etc. and I always get the same error message.
> 
> I would greatly appreciate any help in this matter! Thank you so much
> in advance!
> 
> Yours,
> 
> Paula Sankelo
> 
> PS: I love GRASS, I'm so happy I found it! This is the first serious
> trouble I've run into so far.
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