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

[Jenny Turner]

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?
5- And for each Centroid I select a Cat right?
(Is this the proceeding?)

About this, I have two questions:
a- I have to leave "Insert New record into table" checked right?
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?
c- When I press the image a point is created but how can I define the
boundaries of the centroid?

Thanks
Jenny


On Wed, Jun 9, 2010 at 7:06 PM, Micha Silver <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. +972-52-3665918http://www.surfaces.co.il
>
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