NAME

       v.what.vect  - Uploads vector values at positions of vector points to the table.

KEYWORDS

       vector, sampling, database, position, querying, attribute table

SYNOPSIS

       v.what.vect
       v.what.vect --help
       v.what.vect map=name  [layer=string]  column=name query_map=name  [query_layer=string]  query_column=name
       [dmax=float]   [--help]  [--verbose]  [--quiet]  [--ui]

   Flags:
       --help
           Print usage summary

       --verbose
           Verbose module output

       --quiet
           Quiet module output

       --ui
           Force launching GUI dialog

   Parameters:
       map=name [required]
           Name of vector points map for which to edit attributes
           Or data source for direct OGR access

       layer=string
           Layer number or name
           Vector  features  can have category values in different layers. This number determines which layer to
           use. When used with direct OGR access this is the layer name.
           Default: 1

       column=name [required]
           Name of attribute column to be updated with the query result

       query_map=name [required]
           Name of vector map to be queried
           Or data source for direct OGR access

       query_layer=string
           Layer number or name
           Vector features can have category values in different layers. This number determines which  layer  to
           use. When used with direct OGR access this is the layer name.
           Default: 1

       query_column=name [required]
           Name of attribute column to be queried

       dmax=float
           Maximum query distance in map units
           Default: 0.0

DESCRIPTION

       v.what.vect  transfers  attributes  from  the query_map’s map attribute table into the attribute table of
       points present in the map map. The script is based on v.distance.

NOTES

       The upload column, into which the query results  are  stored,  must  be  present  in  the  map  map.  Use
       v.db.addcolumn to add one if needed.

       Use  dmax  parameter  to control query distance tolerance (how far points/centroids can be from query_map
       features). For more options, use v.distance instead.

       In case of a multipoint input map map, with several points  having  the  same  category  number,  it  can
       happen,  that  the  query  result  is  NULL,  if  the same category number falls into different query_map
       polygons.

       When transferring attributes from a point map to a polygon map, usually dmax has to be larger  than  zero
       (determined by distance between query points and polygon centroids).

       In  case  that  one or both input vector maps are 3D, features need to touch also in the 3rd dimension (z
       coordinate) in order to transfer attributes.

EXAMPLES

       In this example, the ’hospitals’ point map in the North  Carolina  location  is  copied  to  the  current
       mapset,  a  new  attribute  column  is  added  and  the  urban names from the ’urbanarea’ polygon map are
       transferred to the ’myhospitals’ map at the hospital points’ locations:
       g.copy vect=hospitals,myhospitals
       v.db.addcolumn myhospitals column="urb_name varchar(25)"
       v.what.vect myhospitals query_map=urbanarea column=urb_name query_column=NAME
       # verification:
       v.db.select myhospitals

       In this example, city names, population data and more from Geonames.org country files are transferred  to
       selected  EU  CORINE  landuse/landcover classes ("Continuous urban fabric", 111, and "Discontinuous urban
       fabric", 112).  Note: Example in UTM projection to which the input maps have been projected beforehand to
       have metric distances support:
       # extract populated places from geonames
       v.extract geonames_IT where="featurecla=’P’" output=geonames_IT_cities
       # add new column
       v.db.addcol corine_code111_112_cities column="gnameid double precision"
       # transfer geonameid (3000m maximal distance between points and centroids)
       v.what.vect corine_code111_112_cities query_map=geonames_IT_cities column=gnameid \
                   query_column=geonameid dmax=3000
       # now gnameid can be used for v.db.join to join further
       # attributes in from geonames.org

SEE ALSO

        v.db.addcolumn, v.db.select, v.distance, v.rast.stats, v.what.rast, v.what.rast3

AUTHOR

       Markus Neteler

       Last changed: $Date: 2015-10-07 10:15:43 +0200 (Wed, 07 Oct 2015) $

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       © 2003-2016 GRASS Development Team, GRASS GIS 7.0.3 Reference Manual

GRASS 7.0.3                                                                                  v.what.vect(1grass)