[GRASS-user] ouput centroids and areas_newbie

GRASS GRASS user
1

Hello,

New to Grass but not GIS.

I have imported shp file county block group data( tenn_county_new) into a grass mapset. That part is working fine, projections match.

Now I want to output x y coord for all centroids, and areas (in meters) into a table.

I can see centroids and area shows up in the identification so I know its there somewhere.

Tried v.centriod, v.to.db and other options but still have no idea how to do this.

Information in table that is

id
cat
ID (the first three match and just count up the number of blocks)
FIPSSTCO
tractGroup
STFID

Can anyone help?

Matthew

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2

On 09/01/09 17:29, Matthew Mulbrandon wrote:

Hello,

New to Grass but not GIS.

I have imported shp file county block group data( tenn_county_new) into a grass mapset. That part is working fine, projections match.

Now I want to output x y coord for all centroids, and areas (in meters) into a table.

I can see centroids and area shows up in the identification so I know its there somewhere.

Tried v.centriod, v.to.db and other options but still have no idea how to do this.

Information in table that is

id
cat
ID (the first three match and just count up the number of blocks)
FIPSSTCO
tractGroup
STFID

Can anyone help?

Create columns to hold the information in your table with v.db.addcol, i.e.

v.db.addcol map=YourMap column="x double precision"

(repeat for y and area).

Then run v.to.db with

- option=area column=area units=YourChoice
- option=coor column=x,y type=centroid units=YourChoice

Then export table with db.out.ogr or just v.db.select redirected to a file.

Moritz