.TH v.mkgrid 1grass "" "GRASS 7.2.0" "Grass User's Manual"
.SH NAME
\fI\fBv.mkgrid\fR\fR  \- Creates a vector map of a user\-defined grid.
.SH KEYWORDS
vector, geometry, grid, point pattern, hexagon
.SH SYNOPSIS
\fBv.mkgrid\fR
.br
\fBv.mkgrid \-\-help\fR
.br
\fBv.mkgrid\fR [\-\fBha\fR] \fBmap\fR=\fIname\fR  [\fBgrid\fR=\fIrows,columns\fR]   [\fBposition\fR=\fIstring\fR]   [\fBcoordinates\fR=\fIeast,north\fR]   [\fBbox\fR=\fIwidth,height\fR]   [\fBangle\fR=\fIfloat\fR]   [\fBbreaks\fR=\fIinteger\fR]   [\fBtype\fR=\fIstring\fR]   [\-\-\fBoverwrite\fR]  [\-\-\fBhelp\fR]  [\-\-\fBverbose\fR]  [\-\-\fBquiet\fR]  [\-\-\fBui\fR]
.SS Flags:
.IP "\fB\-h\fR" 4m
.br
Create hexagons (default: rectangles)
.IP "\fB\-a\fR" 4m
.br
Allow asymmetric hexagons
.IP "\fB\-\-overwrite\fR" 4m
.br
Allow output files to overwrite existing files
.IP "\fB\-\-help\fR" 4m
.br
Print usage summary
.IP "\fB\-\-verbose\fR" 4m
.br
Verbose module output
.IP "\fB\-\-quiet\fR" 4m
.br
Quiet module output
.IP "\fB\-\-ui\fR" 4m
.br
Force launching GUI dialog
.SS Parameters:
.IP "\fBmap\fR=\fIname\fR \fB[required]\fR" 4m
.br
Name for output vector map
.IP "\fBgrid\fR=\fIrows,columns\fR" 4m
.br
Number of rows and columns in grid
.IP "\fBposition\fR=\fIstring\fR" 4m
.br
Where to place the grid
.br
Options: \fIregion, coor\fR
.br
Default: \fIregion\fR
.br
\fBregion\fR: current region
.br
\fBcoor\fR: use \(cqcoor\(cq and \(cqbox\(cq options
.IP "\fBcoordinates\fR=\fIeast,north\fR" 4m
.br
Lower left easting and northing coordinates of map
.IP "\fBbox\fR=\fIwidth,height\fR" 4m
.br
Width and height of boxes in grid
.IP "\fBangle\fR=\fIfloat\fR" 4m
.br
Angle of rotation (in degrees counter\-clockwise)
.br
Default: \fI0\fR
.IP "\fBbreaks\fR=\fIinteger\fR" 4m
.br
Number of vertex points per grid cell
.br
Options: \fI0\-60\fR
.br
Default: \fI0\fR
.IP "\fBtype\fR=\fIstring\fR" 4m
.br
Output feature type
.br
Options: \fIpoint, line, area\fR
.br
Default: \fIarea\fR
.SH DESCRIPTION
\fIv.mkgrid\fR creates a vector map representation of a regular
coordinate grid. Point, line, and area vector grids can be created.
.SH NOTES
Grid points created with the \fBtype=point\fR option will be placed at
the \fIcenter\fR of each grid cell, like centroids with the default
\fBtype=area\fR option.
.PP
Grid lines created with the \fBtype=line\fR option will be identical to
the edges of each grid cell, like boundaries with the default
\fBtype=area\fR option.
.PP
The resultant grid can be rotated around the origin (center of the
grid) with the \fBangle\fR option.
.PP
Optionally hexagons can be created with the \fB\-h\fR flag. Hexagons
are by default symmetric. Asymmetric hexagons can be allowed with the
\fB\-a\fR flag.
.PP
This module is NOT to be used to generate a vector map of USGS
quadrangles, because USGS quads are not exact rectangles.
.SH EXAMPLES
.SS Creating a global grid in a latitude\-longitude
To be run in a latitude\-longitude location (WGS84)
.br
.nf
\fC
# set the region:
g.region n=90 s=\-90 w=\-180 e=180 res=10 \-p
projection: 3 (Latitude\-Longitude)
zone:       0
datum:      wgs84
ellipsoid:  wgs84
north:      90N
south:      90S
west:       180W
east:       180E
nsres:      10
ewres:      10
rows:       18
cols:       36
cells:      648
# create 10 degree size grid:
v.mkgrid map=grid_10deg
# create 20 degree size grid:
v.mkgrid map=grid_20deg box=20,20
\fR
.fi
.SS Creating a grid in a metric projection
Creating a 4x3 grid, cells 20km a side, with lower left corner at 2716500,6447000:
.br
.nf
\fC
v.mkgrid map=coro_grid grid=4,3 position=coor coordinates=2716500,6447000 box=20000,20000
\fR
.fi
.SS Creating a positioned grid in a latitude\-longitude
Creating a 10x12 lat/lon grid, cells 2 arc\-min a side, with lower left corner
at 167deg 52min east, 47deg 6min south. For use with e.g. QGIS you can then
pull this grid into a projected location with \fIv.proj\fR before
exporting as a Shapefile with \fIv.out.ogr\fR (within GRASS GIS you could
just use \fId.grid \-w\fR from the projected location for the same effect):
.br
.nf
\fC
v.mkgrid map=p2min_grid grid=10,12 position=coor coordinates=167:52E,47:06S box=0:02,0:02
\fR
.fi
.SS Creating a simple point pattern
North Carolina sample dataset example, creating a 1km spaced point grid
based on the current region extent defined by the \(dqelevation\(dq map:
.br
.nf
\fC
g.region raster=elevation res=1000 \-pa
v.mkgrid type=point map=pointpattern
\fR
.fi
.PP
.SS Creating a regular point pattern
North Carolina sample dataset example, creating a regular spaced point grid
based on the current region extent defined by the \(dqelevation\(dq map, using
a two\-step approach:
.br
.nf
\fC
# create first set of points, covering extent of \(dqelevation\(dq raster map
g.region raster=elevation res=1000 \-pa
v.mkgrid type=point map=pointpattern1
# shift grid by half point distance (map units)
g.region n=n+500 w=w+500 e=e+500 s=s+500 \-p
# create second set of points
v.mkgrid type=point map=pointpattern2
# merge into final point pattern
v.patch input=pointpattern1,pointpattern2 output=pointpattern3
\fR
.fi
.br
Different point patterns for sampling design
.SS Creating hexagons in a metric projection
North Carolina sample dataset example, creating regular hexagons
based on the current region extent defined by the \(dqelevation\(dq map and
raster resolution for the hexagon size:
.br
.nf
\fC
g.region raster=elevation res=5000 \-pa
v.mkgrid map=hexagons \-h
d.grid 5000
\fR
.fi
.br
Hexagon map
.SS Using hexagons for point density
To compute point density in a hexagonal grid for the vector map
\fIpoints_of_interest\fR in the basic North Carolina sample dataset,
the vector map itself is used to set extent of the computational region.
The resolution is based on the desired size of hexagons.
.br
.nf
\fC
g.region vector=points_of_interest res=2000 \-pa
\fR
.fi
The hexagonal grid is created as a vector map based on the previously
selected extent and size of the grid.
.br
.nf
\fC
v.mkgrid map=hexagons \-h
\fR
.fi
The following counts the number of points per hexagon using the
\fIv.vect.stats\fR module.
.br
.nf
\fC
v.vect.stats points=points_of_interest areas=hexagons count_column=count
\fR
.fi
User should note that some of the points may be outside the grid
since the hexagons cannot cover all the area around the edges
(the computational region extent needs to be enlarged if all points
should be considered).
The last command sets the vector map color table to viridis
based on the count column.
.br
.nf
\fC
v.colors map=hexagons use=attr column=count color=viridis
\fR
.fi
.br
Point density in a hexagonal grid
.SH SEE ALSO
\fI
d.grid,
v.in.region,
v.patch,
v.vect.stats
\fR
.SH AUTHORS
Michael Higgins,
U.S.Army Construction Engineering
Research Laboratory
.PP
Update for new vectors Radim Blazek 10/2004
.PP
\fILast changed: $Date: 2016\-08\-23 04:07:22 +0200 (Tue, 23 Aug 2016) $\fR
.SH SOURCE CODE
.PP
Available at: v.mkgrid source code (history)
.PP
Main index |
Vector index |
Topics index |
Keywords index |
Graphical index |
Full index
.PP
© 2003\-2016
GRASS Development Team,
GRASS GIS 7.2.0 Reference Manual