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

Andre Joost andre+joost at nurfuerspam.de
Wed Feb 12 15:55:40 EST 2014

Am 12.02.2014 00:33, schrieb Hamish:

>    http://muck.otago.ac.nz/~hamish/sbss/xlat.txt.bz2
>    http://muck.otago.ac.nz/~hamish/sbss/xlong.txt.bz2

I checked it the other way round:

Changed the header of your files to:
> nrows        138
> ncols        138
> xllcorner    0
> yllcorner    0
> cellsize     12000
> NODATA_value -32768

which makes them readable for the GDAL AAIGrid importer.
Then created contour lines from the data, and overlayed it with a WGS84 

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.

Overlaying in QGIS I got this picture:


The cell values around the map center read (from line 75 and 76):

lon:  -77.068146/ -77.057312 / -76.927246 /-76.916199
lat: 40.32201 / 40.313641 / 40.214413 / 40.206055

So CEN_LAT and CEN_LON are just the average of the four middle cells, 
and have nothing to do with the following projection parameters.

Just some more references on the WRF projection parameters:



André Joost

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