## 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) $