[R-sig-Geo] adapting spatial points and wrld_smpl to a reference system implicit in a .nc file

[Alex M]

On 02/22/2016 09:50 AM, Agus Camacho wrote:
> Dear all,
> 
> Im trying to overlap these points:
> https://www.dropbox.com/s/awdclg4cvsdngej/clean%20urosaurus%20records.csv?dl=0
> 
> and a wrld_simpl object:
> library(maptools)
> data(wrld_simpl)
> 
> Over this raster layer
> https://www.dropbox.com/sh/qcw174tgogpnz7s/AAByDc3TeyFe3W4nEqTFix6Oa?dl=0
> 
> This rastr comes from a .nc file without a reference system. The author of
> that .nc file gave me the following data about the .nc.
> 
> The projection is *Lambert conformal conic* projection
> CEN_LAT = 38.0
> CEN_LON = -100.0
> TRUELAT1 = 25.
> TRUELAT2 = 45.
> 
> However, despite i have gone through many sites in the internet, i cant
> figure it out:
> 
> a) if that is all the data i need to set a reference system for my points
> and the wrld_simp object.
> 
> b) how to change a typical CRS object with such data
> 
> Ex.CRS ("+proj=lcc+lat_0=38.0+lon0_2=-100+ellps=WGS84")
> 
> Where do i enter the TRUELAT and CENLAT values?
> Are there any site that explains easily what the fields in the CRS mean and
> how to change them?
> 
> Thanks in advance.
> 

https://github.com/OSGeo/proj.4/wiki/GenParms
https://trac.osgeo.org/proj/wiki/GenParms

I believe:
+lat_0  = CEN_LAT   Latitude of origin
+lat_1  = TRUELAT1   Latitude of first standard parallel
+lat_2  = TRUELAT2   Latitude of second standard parallel
+lon_0  = CEN_LON   Central meridian

proj strings are defined by the proj4 libary. It's website listed above
and the associated mailing lists or gis stackexchange would be the
places to get help on it.
https://lists.osgeo.org/mailman/listinfo/metacrs

It often helps to browse similar projections on
http://spatialreference.org/
http://epsg.io/

Enjoy,
Alex