[Proj] Have LCC center terms, need PROJ.4 terms

Andre Joost andre+joost at nurfuerspam.de
Wed Feb 12 16:41:30 EST 2014

Am 12.02.2014 21:55, schrieb Andre Joost:

> The custom projection I came best with was
> +proj=lcc +lat_1=39.338 +lat_0=39.338 +lon_0=-84 +k_0=1 +x_0=233925
> +y_0=722000 +a=6371229 +b=6371229 +towgs84=0,0,0,0,0,0,0 +units=m +no_defs
> the x_0 value was easy to get, just the distance between left margin and
> the 84° meridian. For y_0, I measured the difference between WGS84 grid
> and the countour lines grid. So, empirical too, but I think you can not
> get much better from a 138x138 cell grid at that resolution.

Ok, now the analytical version ;-)

Put the center coordinates in a text file WRF4326.txt, and perform

cs2cs +init=epsg:4326 +to +proj=lcc +lat_1=39.338 +lat_0=39.338 
+lon_0=-84 +k_0=1 +x_0=0 +y_0=0 +a=6371229 +b=6371229 
+towgs84=0,0,0,0,0,0,0 +units=m +no_defs WRF4326.txt >out.txt

on it. Subtract the result

595747.57	 104990.12

from 828000 (that is 138x1200/2, the center of the raster grid)

and you get

x_0=232252. and y_0=723010.

Almost the same as I got empirical, taking the raster cell size of 
12000m into acount.

André Joost

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