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 (meters for ll)
           Default: 0.0

DESCRIPTION

       v.what.vect transfers attributes from the query_map’s attribute table into the map’s attribute table. The
       module  can  be used to transfer attributes from the table of a polygon map into the attribute table of a
       point vector map, as well as the other way around, i.e., from a point map into the attribute table  of  a
       polygon map (See examples). The script is based on v.distance.

NOTES

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

       Use the dmax parameter to control the query distance tolerance, i.e., how far map’s points/centroids  can
       be from the query_map features.  For further options, use v.distance.

       In case of a multipoint input 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 into a polygon map, dmax has to be larger than zero,  i.e.,
       it  will  be determined by the distance between query points and polygon centroids. Importantly, distance
       is in meters for latitude-longitude locations.

       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 hospital points locations in ’myhospitals’ map:
       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 others from Geonames.org country files are transferred
       to selected EU CORINE landuse/landcover classes ("Continuous urban fabric", 111, and "Discontinuous urban
       fabric",  112).   Note:  The  example  is  in  UTM projection to which the input maps have been projected
       beforehand.
       # 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 from geonames.org

SEE ALSO

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

AUTHOR

       Markus Neteler

SOURCE CODE

       Available at: v.what.vect source code (history)

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       © 2003-2019 GRASS Development Team, GRASS GIS 7.8.2 Reference Manual