[Freegis-list] classification with i.class,i.cluster

[Heiko.Kehlenbrink@vermes.fh-oldenburg.de]

hi list, 
i just got my marks for a homework i did using grass. 
i had to classify several areas in a landsat scene. 
it was the first time that a stundent used grass therefor and i passed. 
usually we had to use pci-works but with about 35 students and only 10 dongles it is a pain... 
some points i like to annotate: 
 
it would be great if one could define a trainingarea assembled out of severeal polygons  
 
we had to identify 6 main classes (water, wood,swamp,rural,grassland and urban) 
afterwards we had to split those classes down to say coniferous forest and deciduous forest. 
 
using i.cluster with the six classes the outcome wasn`t so good, there were many forrest areas 
identified as water, urban areas identified as swamp and so on... 
 
using i.cluster with the subclasses , about 12 basing upon the six main classes, the outcome 
was ok. 
 
in the report generated by i.cluster there was a matrix regarding the seperability of the classes 
but there wasn`t an explanation how to rate the values in the matrix. 
 
all in all it was again very instructional working with grass ... 
 
 
best regards 
 
heiko kehlenbrink