v.select(1grass) | GRASS GIS User's Manual | v.select(1grass) |
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]
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):
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=255:255:50
v.select with OVERLAP operator: selected grid boxes shown in yellow (using GRASS method)
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=255:255:50
v.select with OVERLAPS operator: selected grid boxes shown in yellow (using GEOS method)
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=255:255:50
v.select with DISJOINT operator: selected grid boxes shown in yellow
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=255:255:50
v.select with EQUALS operator: selected grid boxes shown in yellow
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=255:255:50
v.select with INTERSECTS operator: selected grid boxes shown in yellow
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=255:255:50
v.select with TOUCHES operator: selected polygons shown in yellow (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=255:255:50 d.vect map=busroute1 color=200:27:27 width=3
v.select with CROSSES operator: selected polygons shown in yellow (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 yellow (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 yellow (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 yellow (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
Available at: v.select source code (history)
Accessed: Sunday Jan 22 07:37:13 2023
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