NAME

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

KEYWORDS

       vector, geometry, grid, point pattern

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

SEE ALSO

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

AUTHORS

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

       Update for new vectors Radim Blazek 10/2004

       Last changed: $Date: 2014-12-28 00:21:19 +0100 (Sun, 28 Dec 2014) $

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