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v.select(1) Grass User's Manual v.select(1)

v.select - Selects features from vector map (A) by features from other vector map (B).

vector, geometry, spatial query

v.select
 
v.select --help
 
v.select [-tcr] ainput=name [alayer=string] [ atype=string[,string,...]] binput=name [blayer= string] [btype=string[,string,...]] output=name operator= string [relate=string] [--overwrite] [-- help] [--verbose] [--quiet] [--ui]

-t
 
Do not create attribute table
-c
 
Do not skip features without category
-r
 
Reverse selection
--overwrite
 
Allow output files to overwrite existing files
--help
 
Print usage summary
--verbose
 
Verbose module output
--quiet
 
Quiet module output
--ui
 
Force launching GUI dialog

ainput=name [required]
 
Name of input vector map
 
Input vector map from which to select features (A)
alayer=string
 
Layer number (vector map A)
 
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
atype=string[,string,...]
 
Feature type (vector map A)
 
Input feature type
 
Options: point, line, boundary, centroid, area
 
Default: point,line,area
binput=name [required]
 
Name of input vector map
 
Query vector map (B)
blayer=string
 
Layer number (vector map B)
 
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
btype=string[,string,...]
 
Feature type (vector map B)
 
Input feature type
 
Options: point, line, boundary, centroid, area
 
Default: point,line,area
output=name [required]
 
Name for output vector map
operator=string [required]
 
Operator defines required relation between features
 
A feature is written to output if the result of operation ’ainput operator binput’ is true. An input feature is considered to be true, if category of given layer is defined.
 
Options: overlap, equals, disjoint, intersects, touches, crosses, within, contains, overlaps, relate
 
Default: overlap
 
overlap: features partially or completely overlap
 
equals: features are spatially equals (using GEOS)
 
disjoint: features do not spatially intersect (using GEOS)
 
intersects: features spatially intersect (using GEOS)
 
touches: features spatially touches (using GEOS)
 
crosses: features spatially crosses (using GEOS)
 
within: feature A is completely inside feature B (using GEOS)
 
contains: feature B is completely inside feature A (using GEOS)
 
overlaps: features spatially overlap (using GEOS)
 
relate: feature A is spatially related to feature B (using GEOS, requires ’relate’ option)
relate=string
 
Intersection Matrix Pattern used for ’relate’ operator

v.select allows the user to select features from a vector map by features from another one.
Supported operators (without GEOS; using GRASS’ own algorithm):
overlap - features partially or completely overlap (GEOS equivalent: intersects)
Supported operators (internally using GEOS - Geometry Engine, Open Source):
equals - features are spatially equals
disjoint - features do not spatially intersect
intersects - features spatially intersect (equivalent to native ’overlap’)
touches - features spatially touches
crosses - features spatially crosses
within - feature A is completely inside feature B
contains - feature B is completely inside feature A
overlaps - features spatially overlap
relate - feature A is spatially related to feature B

Only features with category numbers will be considered. If required the v.category module can be used to add them. Typically boundaries do not need to be given a category number, as an area’s attributes are inherited from the centroid. Typically points, lines, and centroids will always want to have a cat number. E.g. take a road which separates two farms. It is ambiguous as to which farm an attribute that is attached to the road belongs to. The boundary only needs a cat number if it will hold its own attributes, such as road name or pavement form. A centroid in each paddock holds the information with respect to ownership, area, etc.

Preparation of example data (North Carolina sample dataset):
 
# Create an grid for overlaying to ZIP code vector map
v.mkgrid map=boxgrid grid=10,10 position=coor \
         coordinates=583600,201500 box=5000,5000
# set region to ZIP codes and boxgrid vector maps
g.region vector=zipcodes_wake,boxgrid -p res=100 -a
# enlarge region a bit for "white border" around map in monitor
g.region n=n+1000 s=s-1000 w=w-1000 e=e+1000 -p
d.mon wx0

Select grid boxes (North Carolina sample dataset):
 
d.vect map=zipcodes_wake fill_color=0:128:0
d.vect map=boxgrid fill_color=85:130:176
v.select ainput=boxgrid binput=zipcodes_wake output=v_select_OVERLAP operator=overlap
d.vect map=v_select_OVERLAP
d.vect map=zipcodes_wake type=boundary color=50:50:50
 
v.select with OVERLAP operator: selected grid boxes shown in grey

Select grid boxes (North Carolina sample dataset):
 
d.vect map=zipcodes_wake fill_color=0:128:0
d.vect map=boxgrid fill_color=85:130:176
v.select ainput=boxgrid binput=zipcodes_wake output=v_select_OVERLAPS operator=overlaps
d.vect map=v_select_OVERLAPS
d.vect map=zipcodes_wake type=boundary color=50:50:50
 
v.select with OVERLAPS operator: selected grid boxes shown in grey

Select grid boxes (North Carolina sample dataset):
 
d.vect map=zipcodes_wake fill_color=0:128:0
d.vect map=boxgrid fill_color=85:130:176
v.select ainput=boxgrid binput=zipcodes_wake output=v_select_DISJOINT operator=disjoint
d.vect map=v_select_DISJOINT
d.vect map=zipcodes_wake type=boundary color=50:50:50
 
v.select with DISJOINT operator: selected grid boxes shown in grey

Select zipcode polygon (North Carolina sample dataset):
 
d.vect map=zipcodes_wake fill_color=0:128:0
v.extract input=zipcodes_wake where=ZIPCODE_ID=35 output=zipcodeID35
v.select ainput=zipcodes_wake binput=zipcodeID35 output=v_select_EQUALS operator=equals
d.vect map=v_select_EQUALS
d.vect map=zipcodes_wake type=boundary color=50:50:50
 
v.select with EQUALS operator: selected grid boxes shown in grey

Select zipcode polygons (North Carolina sample dataset):
 
d.vect map=zipcodes_wake fill_color=0:128:0
d.vect map=boxgrid fill_color=85:130:176
v.select ainput=zipcodes_wake binput=boxgrid output=v_select_INTERSECTS operator=intersects
d.vect map=v_select_INTERSECTS
d.vect map=boxgrid type=boundary color=50:50:50
 
v.select with INTERSECTS operator: selected grid boxes shown in grey

Select polygons (North Carolina sample dataset):
 
d.vect map=zipcodes_wake fill_color=0:128:0
d.vect map=zipcodeID35 fill_color=85:130:176
v.select ainput=zipcodes_wake binput=zipcodeID35 output=v_select_TOUCHES operator=touches
d.vect map=v_select_TOUCHES
d.vect map=zipcodes_wake type=boundary color=50:50:50
 
v.select with TOUCHES operator: selected polygons shown in grey (blue: input polygon)

Select zipcode polygons by lines (North Carolina sample dataset):
 
d.vect map=zipcodes_wake fill_color=0:128:0
d.vect map=busroute1 color=200:27:27 width=3
v.select ainput=zipcodes_wake binput=busroute1 output=v_select_CROSSES operator=crosses
d.vect map=v_select_CROSSES
d.vect map=zipcodes_wake type=boundary color=50:50:50
d.vect map=busroute1 color=200:27:27 width=3
 
v.select with CROSSES operator: selected polygons shown in grey (red: input lines)

Select zipcode polygons (North Carolina sample dataset):
 
d.vect map=zipcodes_wake fill_color=0:128:0
d.vect map=boundary_county fill_color=85:130:176
v.select ainput=zipcodes_wake binput=boundary_county output=v_select_WITHIN operator=within
d.vect map=v_select_WITHIN
 
v.select with WITHIN operator: selected polygons shown in grey (blue: input polygons)

Select zipcode polygon (North Carolina sample dataset):

d.vect map=zipcodes_wake fill_color=0:128:0
d.vect map=zipcodeID35 fill_color=85:130:176
v.select ainput=zipcodes_wake binput=zipcodeID35 \
         output=v_select_CONTAINS_pol operator=contains
d.vect map=v_select_CONTAINS
 
v.select with CONTAINS operator: selected polygon shown in grey (blue: input polygon, not visible)

d.vect map=zipcodes_wake fill_color=0:128:0
d.vect map=hospitals fill_color=195:31:31 icon=basic/cross3 size=10
v.select ainput=zipcodes_wake binput=hospitals \
         output=v_select_CONTAINS_pnts operator=contains
d.vect map=v_select_CONTAINS_pnts
d.vect map=hospitals fill_color=195:31:31 icon=basic/cross3 size=10
 
v.select with CONTAINS operator: selected polygons shown in grey (red: input points) This operator additionally requires the relate parameter (in other GIS called ’ST_Relate’). This operator allows calculating the Dimensionally Extended nine-Intersection Model (DE-9IM). In the following one example: Select polygon with ’TOUCHES’ operator (North Carolina sample dataset):
 
d.vect map=zipcodes_wake fill_color=0:128:0
d.vect map=zipcodeID35 fill_color=85:130:176
v.select ainput=zipcodeID35 binput=zipcodes_wake \
         output=v_select_TOUCHES_relate operator=relate relate=’T********’
d.vect map=v_select_TOUCHES
The result of relate=’T********’ is the same as seen above in the example ’TOUCHES’. See the DE-9IM page for related operators and their definition.

Extract fire stations (points) falling into urban area (polygon) - North Carolina data set (point in polygon test):
 
v.select ainput=firestations binput=urbanarea output=urban_firestations \
         operator=overlap

Extract railroad lines from zip code map overlapping with the urban area (line in polygon test):
 
v.select ainput=railroads binput=urbanarea \
         output=railroads_in_urbanarea operator=overlap

Extract those areas from zip code map which overlap with railroads (polygon on line test):
 
# first add a tiny buffer around railroad lines:
v.buffer input=railroads output=railroads_buf20m \
  distance=20
v.select ainput=zipcodes_wake binput=railroads_buf20m \
  output=zipcodes_wake_railroads operator=overlap

v.category, v.clip, v.overlay, v.extract
GRASS SQL interface
 
GEOS - Geometry Engine, Open Source

Radim Blazek
 
GEOS support by Martin Landa, Czech Technical University in Prague, Czech Republic
 
ZIP code examples by Carol X. Garzon-Lopez, Trento, Italy
Last changed: $Date: 2018-03-19 22:57:45 +0100 (Mon, 19 Mar 2018) $

Available at: v.select source code (history)
Main index | Vector index | Topics index | Keywords index | Graphical index | Full index
© 2003-2018 GRASS Development Team, GRASS GIS 7.4.3 Reference Manual
GRASS 7.4.3

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