v.what.vect(1grass)

1v.what.vect(1)                Grass User's Manual               v.what.vect(1)
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NAME

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

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

13       v.what.vect
14       v.what.vect --help
15       v.what.vect  map=name    [layer=string]    column=name   query_map=name
16       [query_layer=string]     query_column=name    [dmax=float]     [--help]
17       [--verbose]  [--quiet]  [--ui]
18
19   Flags:
20       --help
21           Print usage summary
22
23       --verbose
24           Verbose module output
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26       --quiet
27           Quiet module output
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29       --ui
30           Force launching GUI dialog
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32   Parameters:
33       map=name [required]
34           Name of vector points map for which to edit attributes
35           Or data source for direct OGR access
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37       layer=string
38           Layer number or name
39           Vector features can have category values in different layers.  This
40           number  determines  which  layer  to use. When used with direct OGR
41           access this is the layer name.
42           Default: 1
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44       column=name [required]
45           Name of attribute column to be updated with the query result
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47       query_map=name [required]
48           Name of vector map to be queried
49           Or data source for direct OGR access
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51       query_layer=string
52           Layer number or name
53           Vector features can have category values in different layers.  This
54           number  determines  which  layer  to use. When used with direct OGR
55           access this is the layer name.
56           Default: 1
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58       query_column=name [required]
59           Name of attribute column to be queried
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61       dmax=float
62           Maximum query distance in map units (meters for ll)
63           Default: 0.0
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DESCRIPTION

66       v.what.vect transfers attributes from the query_map’s map attribute ta‐
67       ble  into  the  attribute  table  of points present in the map map. The
68       script is based on v.distance.
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NOTES

71       The upload column, into which the query results  are  stored,  must  be
72       present in the map map. Use v.db.addcolumn to add one if needed.
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74       Use  dmax  parameter  to  control  query  distance  tolerance  (how far
75       points/centroids can be from query_map features). For more options, use
76       v.distance instead.
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78       In  case  of a multipoint input map map, with several points having the
79       same category number, it can happen, that the query result is NULL,  if
80       the same category number falls into different query_map polygons.
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82       When transferring attributes from a point map to a polygon map, usually
83       dmax has to be larger than zero (determined by distance  between  query
84       points and polygon centroids).
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86       In  case  that  one  or both input vector maps are 3D, features need to
87       touch also in the 3rd dimension (z coordinate)  in  order  to  transfer
88       attributes.
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EXAMPLES

91       In  this example, the ’hospitals’ point map in the North Carolina loca‐
92       tion is copied to the current mapset, a new attribute column  is  added
93       and the urban names from the ’urbanarea’ polygon map are transferred to
94       the ’myhospitals’ map at the hospital points’ locations:
95       g.copy vect=hospitals,myhospitals
96       v.db.addcolumn myhospitals column="urb_name varchar(25)"
97       v.what.vect myhospitals query_map=urbanarea column=urb_name query_column=NAME
98       # verification:
99       v.db.select myhospitals
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101       In this example, city names, population data and more from Geonames.org
102       country  files  are transferred to selected EU CORINE landuse/landcover
103       classes ("Continuous urban fabric", 111, and "Discontinuous urban  fab‐
104       ric",  112).   Note:  Example in UTM projection to which the input maps
105       have been projected beforehand to have metric distances support:
106       # extract populated places from geonames
107       v.extract geonames_IT where="featurecla=’P’" output=geonames_IT_cities
108       # add new column
109       v.db.addcol corine_code111_112_cities column="gnameid double precision"
110       # transfer geonameid (3000m maximal distance between points and centroids)
111       v.what.vect corine_code111_112_cities query_map=geonames_IT_cities column=gnameid \
112                   query_column=geonameid dmax=3000
113       # now gnameid can be used for v.db.join to join further
114       # attributes in from geonames.org
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AUTHOR

121       Markus Neteler
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123       Last changed: $Date: 2016-08-22 04:16:33 +0200 (Mon, 22 Aug 2016) $
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SOURCE CODE

126       Available at: v.what.vect source code (history)
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128       Main  index  | Vector index | Topics index | Keywords index | Graphical
129       index | Full index
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131       © 2003-2019 GRASS Development Team, GRASS GIS 7.4.4 Reference Manual
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135GRASS 7.4.4                                                     v.what.vect(1)