1v.what.vect(1) Grass User's Manual v.what.vect(1)
2
6 v.what.vect - Uploads vector values at positions of vector points to
7 the table.
8
10 vector, sampling, database, position, querying, attribute table
11
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 Flags:
20 --help
21 Print usage summary
22 --verbose
24 Verbose module output
25 --quiet
27 Quiet module output
28 --ui
30 Force launching GUI dialog
31 Parameters:
33 map=name [required]
34 Name of vector points map for which to edit attributes
35 Or data source for direct OGR access
36 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
43 column=name [required]
45 Name of attribute column to be updated with the query result
46 query_map=name [required]
48 Name of vector map to be queried
49 Or data source for direct OGR access
50 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
57 query_column=name [required]
59 Name of attribute column to be queried
60 dmax=float
62 Maximum query distance in map units (meters for ll)
63 Default: 0.0
64
66 v.what.vect transfers attributes from the query_map’s attribute table
67 into the map’s attribute table. The module can be used to transfer
68 attributes from the table of a polygon map into the attribute table of
69 a point vector map, as well as the other way around, i.e., from a point
70 map into the attribute table of a polygon map (See examples). The
71 script is based on v.distance.
72
74 The upload column into which the query results are stored must be
75 present in map. Use v.db.addcolumn to add one if needed.
76 Use the dmax parameter to control the query distance tolerance, i.e.,
78 how far map’s points/centroids can be from the query_map features. For
79 further options, use v.distance.
80 In case of a multipoint input map with several points having the same
82 category number, it can happen that the query result is NULL if the
83 same category number falls into different query_map polygons.
84 When transferring attributes from a point map into a polygon map, dmax
86 has to be larger than zero, i.e., it will be determined by the distance
87 between query points and polygon centroids. Importantly, distance is in
88 meters for latitude-longitude locations.
89 In case that one or both input vector maps are 3D, features need to
91 touch also in the 3rd dimension (z coordinate) in order to transfer
92 attributes.
93
95 In this example, the ’hospitals’ point map in the North Carolina loca‐
96 tion is copied to the current mapset, a new attribute column is added
97 and the urban names from the ’urbanarea’ polygon map are transferred to
98 hospital points locations in ’myhospitals’ map:
99 g.copy vect=hospitals,myhospitals
100 v.db.addcolumn myhospitals column="urb_name varchar(25)"
101 v.what.vect myhospitals query_map=urbanarea column=urb_name query_column=NAME
102 # verification:
103 v.db.select myhospitals
104 In this example, city names, population data and others from Geon‐
106 ames.org country files are transferred to selected EU CORINE lan‐
107 duse/landcover classes ("Continuous urban fabric", 111, and "Discontin‐
108 uous urban fabric", 112). Note: The example is in UTM projection to
109 which the input maps have been projected beforehand.
110 # extract populated places from geonames
111 v.extract geonames_IT where="featurecla=’P’" output=geonames_IT_cities
112 # add new column
113 v.db.addcol corine_code111_112_cities column="gnameid double precision"
114 # transfer geonameid (3000m maximal distance between points and centroids)
115 v.what.vect corine_code111_112_cities query_map=geonames_IT_cities column=gnameid \
116 query_column=geonameid dmax=3000
117 # now gnameid can be used for v.db.join to join further
118 # attributes from geonames.org
119
121 v.db.addcolumn, v.db.select, v.distance, v.rast.stats, v.what.rast,
122 v.what.rast3, v.vect.stats
123
125 Markus Neteler
126 Last changed: $Date: 2018-08-03 20:49:03 +0200 (Fri, 03 Aug 2018) $
128
130 Available at: v.what.vect source code (history)
131 Main index | Vector index | Topics index | Keywords index | Graphical
133 index | Full index
134 © 2003-2019 GRASS Development Team, GRASS GIS 7.6.0 Reference Manual
136GRASS 7.6.0 v.what.vect(1)