[GRASS-user] creating vector grids (especially associated with projections)

[Hamish]

Patrice wrote:
> But for other grids, like a non regular lon lat grid (more precise in
> the middle)

nested or non-linear?

> or for a lambert conformal 'natural' grid (which are the examples
> I have) or any other grid that could arise, is there a simple way to do
> a vector corresponding with that grid?

try the v.mkgrid module. then use v.proj to pull it into the other
projection.

in LCC or some other projection you can run d.grid, and "d.grid -w" to
get both local grid and lat/lon grid over the top of each other.

neither v.mkgrid or d.grid are very happy with 180 longitude, but using
0-360 instead of -180 to +180 can help there. (?)

> If not, are there some code somewhere that helps doing geometric vectors,
> like grids (but one could also imagine doing circles and so on)

see the GRASS raster screenshots page for polar stereographic projection
with a lat/lon grid made by v.mkgrid reprojected into the local projection.
(making circles around the poles)


> Something like a high level API to do vector geometries, and not
> something where you have to enter every coordinate and curve
> informations?

create SVG in Inkscape, save as DXF, import DXF into GRASS.


> Also are you aware of people interested in such developments, are there
> library of vector code/features/scripting or similar in the open source 
> GIS community?

for really sophisticated mesh grids have a look at Pavel Sakov's tools:
   http://code.google.com/u/pavel.sakov/
and the front-end to that Octant:
   http://code.google.com/p/octant/


good luck,
Hamish