I have just developed a new GRASS module v.mkgeogrid to meet a in-house
need. v.mkgeogrid is an extension program from v.mkquads which was written by
Micheal Higgins of CERL.
What v.mkgeogrid does ?
It creats a geographic (lat, long) grid vector (and site_list) file with
user defined geographic unit (in minutes) and origin (lat,long). For example,
you could create a 2 degree X 1 degree grid vector with 10 minutes interval.
What is the difference between v.mkgrid and v.mkgeogrid ?
v.mkgrid generates grid on a projected surfce (i.e. UTM), The algorithm
is based upon a (2-D) plane surface. The map unit will be in a projection unit
(meter, feet, etc...).
v.mkgeogrid generates grid on the basis of geographic shape of the earth
by using lat, long coordinates, then project into UTM. The grid will refelect
the lat, long grids (projected into GRASS UTM location).
The source code of v.mkgeogrid is modified from the codes of both
v.mkquads and v.mkgrid.
Syntax:
Usage:
v.mkgeogrid [-esrv] map=name unit=value grid=rows,columns
origin=latitude, longitude
Flags:
-e encompass current window with quads
-s create sites file
-r create region file(s): quad.1 quad.2 ...
-v create vector file (default)
Parameters:
map map name
unit unit in minute
grid Number of rows and columns in grid
origin Latitude and longitude of origin
Once I write a doc for v.mkgeogrid, the source code will be copied to
the "grass/incoming" directory on moon.
Song Wang
wang@cast.uark.edu
Phone: (501) 575 6159