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NAME

       v.mkgrid  - Creates a vector map of a user-defined grid.

KEYWORDS

       vector, geometry, grid, point pattern, hexagon

SYNOPSIS

       v.mkgrid
       v.mkgrid --help
       v.mkgrid        [-ha]        map=name        [grid=rows,columns]         [position=string]
       [coordinates=east,north]      [box=width,height]      [angle=float]       [breaks=integer]
       [type=string]   [--overwrite]  [--help]  [--verbose]  [--quiet]  [--ui]

   Flags:
       -h
           Create hexagons (default: rectangles)

       -a
           Allow asymmetric hexagons

       --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

   Parameters:
       map=name [required]
           Name for output vector map

       grid=rows,columns
           Number of rows and columns in grid

       position=string
           Where to place the grid
           Options: region, coor
           Default: region
           region: current region
           coor: use ’coor’ and ’box’ options

       coordinates=east,north
           Lower left easting and northing coordinates of map

       box=width,height
           Width and height of boxes in grid

       angle=float
           Angle of rotation (in degrees counter-clockwise)
           Default: 0

       breaks=integer
           Number of vertex points per grid cell
           Options: 0-60
           Default: 0

       type=string
           Output feature type
           Options: point, line, area
           Default: area

DESCRIPTION

       v.mkgrid  creates  a  vector map representation of a regular coordinate grid. Point, line,
       and area vector grids can be created.

NOTES

       Grid points created with the type=point option will be placed at the center of  each  grid
       cell, like centroids with the default type=area option.

       Grid  lines  created with the type=line option will be identical to the edges of each grid
       cell, like boundaries with the default type=area option.

       The resultant grid can be rotated around the origin (center of the grid)  with  the  angle
       option.

       Optionally  hexagons  can  be created with the -h flag. Hexagons are by default symmetric.
       Asymmetric hexagons can be allowed with the -a flag.

       This module is NOT to be used to generate a vector map of USGS quadrangles,  because  USGS
       quads are not exact rectangles.

EXAMPLES

   Creating a global grid in a latitude-longitude
       To be run in a latitude-longitude location (WGS84)
       # 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

   Creating a grid in a metric projection
       Creating a 4x3 grid, cells 20km a side, with lower left corner at 2716500,6447000:
       v.mkgrid map=coro_grid grid=4,3 position=coor coordinates=2716500,6447000 box=20000,20000

   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  v.proj  before  exporting as a Shapefile with v.out.ogr (within
       GRASS GIS you could just use d.grid -w from the projected location for the same effect):
       v.mkgrid map=p2min_grid grid=10,12 position=coor coordinates=167:52E,47:06S box=0:02,0:02

   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 "elevation" map:
       g.region raster=elevation res=1000 -pa
       v.mkgrid type=point map=pointpattern

   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 "elevation" map, using a two-step approach:
       # create first set of points, covering extent of "elevation" 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
       Different point patterns for sampling design

   Creating hexagons in a metric projection
       North Carolina sample dataset example, creating regular  hexagons  based  on  the  current
       region extent defined by the "elevation" map and raster resolution for the hexagon size:
       g.region raster=elevation res=5000 -pa
       v.mkgrid map=hexagons -h
       d.grid 5000
       Hexagon map

   Using hexagons for point density
       To  compute point density in a hexagonal grid for the vector map points_of_interest 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.
       g.region vector=points_of_interest res=2000 -pa
       The  hexagonal grid is created as a vector map based on the previously selected extent and
       size of the grid.
       v.mkgrid map=hexagons -h
       The following counts the number of points per hexagon using the v.vect.stats module.
       v.vect.stats points=points_of_interest areas=hexagons count_column=count
       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.
       v.colors map=hexagons use=attr column=count color=viridis
       Point density in a hexagonal grid

SEE ALSO

        d.grid, v.in.region, v.patch, v.vect.stats

AUTHORS

       Michael Higgins, U.S.Army Construction Engineering Research Laboratory

       Update for new vectors Radim Blazek 10/2004

       Last changed: $Date: 2016-08-23 04:00:20 +0200 (Tue, 23 Aug 2016) $

SOURCE CODE

       Available at: v.mkgrid source code (history)

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       © 2003-2019 GRASS Development Team, GRASS GIS 7.6.1 Reference Manual