bionic (1) v.what.vect.1grass.gz

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, v.vect.stats

AUTHOR

       Markus Neteler

       Last changed: $Date: 2016-08-22 04:16:33 +0200 (Mon, 22 Aug 2016) $

SOURCE CODE

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

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       © 2003-2018 GRASS Development Team, GRASS GIS 7.4.0 Reference Manual