[GRASS-user] Using Tck/tk vector digitizer for training areas

[Micha Silver]

On 06/16/2010 06:55 PM, Jenny Turner wrote:
> Hi Micha and GRASS-users/list
>
> Let me see if I get this straight
> 1- use v.digit (e.g. v.digit -n map=vector00 bgcmd=d.rast 
> map=lsat5_1987_40 )
> 2- Inside tcltk's digitizing menu select Digitize new Centroid
> 3- Leave layer as 1?
> 4- Change Mode to Manual Entry?
All the above looks good.
> 5- And for each Centroid I select a Cat right?
Yes, always using the *same* cat for training areas of the same type.
> (Is this the proceeding?)
>
> About this, I have two questions:
> a- I have to leave "Insert New record into table" checked right?
Yes
> b- After I left "Insert New record into table" checked, Layer 1 and 
> Cat 1 and Mode: Manual Entry, when I presss in the image a Error 
> Window appeared stating: Database table for this layer is not defined. 
> Where shall i define the database table for a new vectorial that I 
> digitizing?
Ah, v.db.addtable vector00 col="train_lbl varchar(16), GRASSRGB varchar(16)"
THis should setup an attrib table with two columns, one for a label and 
one for an RGB color for the training area.
> c- When I press the image a point is created but how can I define the 
> boundaries of the centroid?
First digitize the boundary. Here you need not enter any attributes. The 
cat values are also not relevant.
NExt digitize a centroid inside each boundary. Give each centroid a cat 
value that matches the type of training area. So all the forests will be 
i.e cat=1, and all the urban will be i.e cat=10, etc.

>
> Thanks
> Jenny
>
>
> On Wed, Jun 9, 2010 at 7:06 PM, Micha Silver <micha at arava.co.il 
> <mailto:micha at arava.co.il>> wrote:
>
>>     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
>
>
>
>
> This mail was received via Mail-SeCure System.


-- 
Micha Silver
Arava Development Co. +972-52-3665918
http://surfaces.co.il


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