[GRASS-user] Using Tck/tk vector digitizer for training areas
Micha Silver
micha at arava.co.il
Thu Jun 17 15:50:49 EDT 2010
On 06/17/2010 12:36 PM, Jenny Turner wrote:
> Thanks Micha for your help but I got an error while doing this
>
> 1- Create new empty vectorial
> 2- run v.db.addtable command that you kindly sent me
> 3- use v.digit as defined previously
> 4- Inside tcltk's digitizing menu select Digitize new Centroid
> 5- Leave layer as 1
> 6- Change Mode to Manual Entry
> 7- First digitize boundary (by selecting boundary) by selecting points
> with left-mouse-button and close polygon with right-mouse-button
> 8- A panel with "FORM" title appears with a tab saying Attributes
> saying: "New record was created" saying CAT : 1 (this cat refers to
> the land cover category right?); train_lbl value and GRASSRGB;
> 9- I place the values (water,1) for train_lbl and GRASSRGB
> 10- a box ask me for "ASSUME DATA ENCODING AS" a list appears. I
> should select which one? ASCII?
> 11- In trhis case I select ASCII and press SUBMIT. In the bottom of
> that box "Record successfully updated" appeared.
> 12- Insert centroid-1 and press submit in "Form" panel
> 13- Did the same for a few more polygons of cat 1
> 14- Did the same for a few more polygons of cat 2 and 3
> 15- Pressed Save and Exit
>
> Then I realized that at my v.digit panel command output I had this
> warning in there:
> *Could not set Tcl system encoding to 'ascii' (unknown encoding "ascii")*
> *Unable to read vector map*
>
> Questions:
> 1- Is this the right procedure?
Yes. I'd just add one thing that might make the work easier. You don't
need to enter the label and GRASSRGB for each centroid. Just leave them
blank. Then, when you're all finished digitizing, you can run an update
such as:
echo 'UPDATE vector06 SET train_lbl="Forest" WHERE cat=1' | db.execute
echo 'UPDATE vector06 SET GRASSRGB="0:255:0" WHERE cat=1' | db.execute
(The second line will set the GRASSRGB column to green )
> 2- What encoding should I use?
Perhaps try Latin1
> 3- Regarding GRASSRGB field, what information usually you place in
> there? Color code or color description?
The format is a text string containing three numbers <=255 separated by
':'. So i.e. "128:128:128" is medium gray.
> 4- For Supervised classification algorithms in GRASS, Vector type
> (accessible by using Query raster/vector tool) should be Boundary?
> Because, for instance, if I press a defined boundary, in some places I
> get Type: AREA and in others: Boundary (as shown bellow)
AFAIK, each of the classification algorithms needs a *raster* map of
training areas. So your next step, after finishing the vector map of
training areas, will be to convert it to raster. So you'll be doing
something like:
v.to.rast vector06 out=train06 use=cat type=area
Now the cat value that will be used for each raster pixels inside a
vector area is the cat value of the *centroid*. Again, the boundary in
GRASS's topological vector structure is not relevant to the enclosed
area's attributes. You can, if you want, give the boundary the same cat
value, and same GRASSRGB as the centroid. Then, if you use this column
to color the vector when displaying the map, the boundary and the filled
area will be in the same color. But for classification, when you convert
the vector training areas to raster, what will be used is the *centroid*
cat value.
> (...)
> Map: vector06
> Mapset: landsat
> Type: Boundary
> Id: 9
> Layer: 1
> Category: 3
> Driver: dbf
> Database: C:\GRASS6\grassdata/North-Carolina/landsat/dbf/
> Table: vector06
> Key column: cat
> cat : 3
> train_lbl : urban
> GRASSRGB : 3
> (Thu Jun 17 10:34:04 2010) Command finished (0 sec)
> (Thu Jun 17 10:34:06 2010)
> v.what --q -a map=vector06 at landsat east_north=639279.744997,227730.071998
> (...)
> Map: vector06
> Mapset: landsat
> Type: Area
> Sq Meters: 2158429.741
> Hectares: 215.843
> Acres: 533.360
> Sq Miles: 0.8334
> Layer: 1
> Category: 3
> Driver: dbf
> Database: C:\GRASS6\grassdata/North-Carolina/landsat/dbf/
> Table: vector06
> Key column: cat
> cat : 3
> train_lbl : urban
> GRASSRGB : 3
>
> Thanks for your help and support
>
> Jenny
>
>
>
> On Wed, Jun 16, 2010 at 7:59 PM, Micha Silver <micha at arava.co.il
> <mailto:micha at arava.co.il>> wrote:
>
> 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
>
>
>
>
>
> This mail was received via Mail-SeCure System.
--
Micha Silver
Arava Development Co. +972-52-3665918
http://surfaces.co.il
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