On 06/09/2010 07:48 PM, Jenny Turner wrote:
Greetings
I'm using WinGRASS (from OSGEO4W installer) to do some supervised
classification. Since I'm using winGRASS i.class function is not
available neither wxGUI's vector digitizer. So I'm using tcl/tk but
I'm a bit confused on using it.
About the background images I used a discussion from last week
regarding this but now.. How can I define a category? I mean, How can
atribute a polygon to a certain category?
This indeed is not obvious. What I've done is change the category mode
from "Next not used" to "Manual entry". This is set in the lower part of
the v.digit window (in tcltk interface). Now each time you digitize a
*centroid* for a training area, set its cat value to some standard value
you choose. For example, you might decide:
train_area cat
------------------------
forest 1
agriculture 2
urban 9
water 10
....
Now for each training polygon which is a forest, set the cat value of
its centroid to 1, agri areas will get value 2, and so on for all the
centroids of all the training polygons. (Note that the cat values for
the boundary lines are pretty much irrelevant in GRASS's vector model).
When you're done digitizing training areas, you might add another column
or two to the attrib table for the training areas -
v.db.addcol train_areas col="train_label varchar(16), RGBCOLOR varchar(16)"
then give each centroid cat value a suitable label and an RGB color
combo, etc. Makes life easier down the line...
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--
Micha Silver
Arava Development Co. +972-52-3665918
http://www.surfaces.co.il
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