[GRASS-web] Issues with i.segment.uspo

[Moritz Lennert]

Hi Dan,

On 26/10/18 13:06, Markus Neteler wrote:
> Dan,
> 
> Alexander, Daniel (PG) <D.Alexander at edu.salford.ac.uk 
> <mailto:D.Alexander at edu.salford.ac.uk>> schrieb am Fr., 26. Okt. 2018, 
> 13:04:
> 
>     To whom this may concern,
> 
> 
>     I am currently trying to use the i.segment.uspo tool for obia on a
>     high resolution data set. However I keep recieving the following error:
> 
> 
>     ValueError: max() arg is an empty sequence
> 
> 
>     I am carrying out the classification in the Grass UI. Could you
>     provide me with any guidance, or possibly redirect me to soem resources?
> 
> 
>     Many thanks,
> 
>     Dan
> 
> 
> So you use a recent version? Just to be sure the we speak about the 
> current i.segment.uspo.

I just (1 min ago) committed a fix to i.segment.uspo which should handle 
this case. Please reinstall the module using g.extension. If you work 
with MS Windows, you will have to wait for it a bit to become available 
(max 24h).

This said, this error generally happens when one of the segmentation 
levels asked for leads to a result with one single segment. This depends 
on your image, the threshold range you are testing, but also the region 
you are working with.

It would help if you gave us some info about the data:

- output of g.region -p
- output of g.region region=OneOfYourTestRegions -up
- output of r.info on one of the bands you are using
- the call you used for i.segment.uspo - you should be able to find the 
command line used in the GUI "Command console" by using the up arrow - 
or once you have filled in all the fields in the module GUI, just click 
on the "Copy" button to copy the command line to the clipboard.

Moritz