[ncl-talk] plot spatial distribution of BELD3 data

[Rick Brownrigg]

Hi Xiaoming,

Yes, NCL could interpret this -- in principle -- but not without more
information.  The data appear to be in a projected coordinate space.  See
the examples at

    http://ncl.ucar.edu/Applications/native.shtml

The precise cartographic projection parameters are not immediately evident
from the metadata given above, although we can make some guesses (it would
be better to know for certain!).

These parameters:
                :XCENT = -90. ;
                :YCENT = 40. ;
                :XORIG = -1296000. ;
                :YORIG = -1404000. ;
                :XCELL = 1000. ;
                :YCELL = 1000. ;

XCELL/YCELL affirm the data are at 1 1km spacing. The XCENT/YCENT and
XORIG/YORIG give the correspondence between the projected and geographical
spaces for the geographical location 90W/40N, a central location in North
America.

These parameters:

                :P_ALP = 30. ;
                :P_BET = 60. ;
                :P_GAM = -90. ;

Looking at some of the maps at the EPA site you reference, these could very
well be projection parameters for a Lambert Conformal projection, with
P_ALP/P_BET being more commonly referred to as "standard parallels"  and
P_GAM being the "standard meridian". The values look quite right for North
America, but again all of this is conjecture.

Hope this helps...
Rick

On Thu, Feb 7, 2019 at 5:08 AM xiaoming Hu <yuanfangcan at hotmail.com> wrote:

> I try to plot spatial distribution of BELD data from
> https://www.epa.gov/air-emissions-modeling/biogenic-emissions-landuse-database-version-3-beld3
>
> the NetCDF files don't provide latitude/longitude, only with information of
>                 :P_ALP = 30. ;
>                 :P_BET = 60. ;
>                 :P_GAM = -90. ;
>                 :XCENT = -90. ;
>                 :YCENT = 40. ;
>                 :XORIG = -1296000. ;
>                 :YORIG = -1404000. ;
>                 :XCELL = 1000. ;
>                 :YCELL = 1000. ;
>                 :VGTYP = -9999 ;
>                 :VGTOP = -9.e+36f ;
>                 :VGLVLS = 0.f, 0.f ;
>                 :GDNAM = "BELD3_TILE9     " ;
>
> It there anyway NCL could interpret this ?
>
> Thanks
> Xiaoming
>
>
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