[GRASS-user] Mapping Africa in an equal area projection

[Hamish]

Corrado wrote:
> I would like to use it to map distribution of some specimen
> at a resolution of 100 km x 100 km (or even down to 25 km x 25 km).
> 
> I gathered some information, and ended up with:
> 
> 1) Sinusoidal
> 2) Equatorial Lambert Azimuthal Equal Area
> 3) Albers Equal Area (Conic)
> 4) Mollweide
> 5) Cylindrical Equal Area
> 
> I do not really know which one to choose. What do you
> recommend?

I would suggest to ask on the PROJ.4 mailing list.  http://proj.osgeo.org

 
> For each of them, which ellipsoid  and datum would you choose?

if you are creating something custom probably stick with WGS84.



as for your point data, you can import it into a lat/lon WGS84 location
(epsg:4326) as points with v.in.ascii. once you have set up your new
projection you can pull that file over with v.proj. r.in.xyz wants a
text file as input, so you'd have to re-export (with projected coords
this time) with v.out.ascii.db (from wiki addons) or v.out.ascii + a
little cut & paste in a spreadsheet.

alternatively you can reproject your text file from lat/lon WGS84 to
(whatever) with the 'm.proj -i' module from within the new projection,
or cs2cs from proj4.

if using v.in.ascii to create a points map some stuff to play with is
v.kernel and v.surf.rst.


Hamish