[GRASS-stats] creating a grid from a contour vector shape

[Mauricio Zambrano]

Hi Alex,

Did you try the commands 'spsample' in R ?

For creating the grid form the shapefile, you can try something like:

yourgrid <- spsample(yourshafilename.shp, type="regular",
cellsize=yourcellsize, offset = c(0.5, 0.5))

I hope this helps.

Kinds,

Mauricio
-- 
Linux user  #454569 -- Ubuntu user #17469

2009/9/5 alexandre villers <alexandre.villers at cebc.cnrs.fr>:
> Good evening,
>
> I'm a beginner with GRASS. In order to analyse a dataset on the spatial distribution of a bird's species, I wanted to create many spatial grids (with increasing cell size, from 500 to 15000 meters)and then count birds in each cell.
>
> I started with
> v.in.ogr to import a countour shape file for my observation window
> v.to.rast (countour)followed by r.mask to limit the work on that contour limit
> finally, v.mkgrid to create the grid with the required spatial resolution.
>
> I'm looping this with R and also added 10 different origins (lower left corner of grids) in order to average counts, specially for large grids.
>
> The next step is to overlay within R, using the sp packages, the layer of points and the grid. The problem (which, by taking the time of reflexion, would have been clear before running the script !) is that some grid cells are cut many times by the countour vector, leading to unique cells having many different IDs (which I didn't want).
>
> So can I overlay that contour vector on a grid while keeping the cells (intact) intersected by the countour limit (instead of clipping them) ?
>
> Hope I was clear enough...
>
> Best regards
>
> Alex
> Alexandre Villers
> PhD. Student
> Team Biodiversity
> CEBC CNRS
> 79360 Beauvoir sur Niort
>
>
> __________ Information from ESET Mail Security, version of virus signature database 4398 (20090905) __________
>
> The message was checked by ESET Mail Security.
> http://www.eset.com
>
>
> _______________________________________________
> grass-stats mailing list
> grass-stats at lists.osgeo.org
> http://lists.osgeo.org/mailman/listinfo/grass-stats
>