[RegCNET] Deciphering OUT_HEAD.CTL

[Maurice.McHugh at noaa.gov]

Hello everyone,

I'm trying to understand why in OUT_HEAD.CTL the pdef line states my correct grid sizes (nx,ny), but the xdef and ydef lines which should state the same grid size are different.

For example,
<snip>
pdef   58   58 lcc   38.89  -77.00   29.00   29.00   30.00   60.00  -77.00  10000.  10000.
xdef  166 linear  -80.65  0.0450
ydef  126 linear   36.11  0.0450
</snip>

In the above case the 58x58 nature of my grid is correctly specified in pdef, but not in xdef nor ydef which give a 166x126 grid.  

In order to better understand the file I went ahead converted the data to netCDF using CDO (climate data operators) and plotted markers at the intersection of xlong and xlat from OUT_HEAD.CTL but when plotted they produced a straight line.  I'm unsure whether this is a CDO translation artifact, or if my understanding of the contents of the OUT_HEAD.CTL file is woefully inadequate.

Any insight to correctly extracting usable data from this file would be much appreciated!

Regards,

Maurice