[Vis5d-users] FW: lambert conformal

Hi Giovanni - it looks like the problem resides in the value for
proj_args(3). 
This represents the row of the nearest pole (in this case, north), if the
pole 
were located on a larger, superimposed grid of the same scale.  Looking at
the 
corner points of the grid:

                             North Pole
                          90.000N, 95.000W
                            (53,178.745)





     54.536N, 152.856W  ----------------------  57.290N, 49.385W
         (1,65)                                     (93,65)
           |                                           |
           |                                           |
           |                                           |
     12.190N, 133.459W  ----------------------  14.335N, 65.091W
         (1,1)                                       (93,1)

Since the pole is at 90N, even with the curvature of the earth in the LC
grid, 
we can see that it would not, in fact, reside on this particular grid.
Vis5d 
starts counting the rows at the top, not the bottom.  As a result, for the
North Pole, the following equation comes in to play:

pole_row = (rows - 1) - pole_row

So you should end up with the following:

nr = 65
nc = 93

projection = 2

proj_args(1) = 25.0
proj_args(2) = 25.0
proj_args(3) = -114.745
proj_args(4) = 53.0
proj_args(5) = 95.0     // this one may be -95.0
proj_args(6) = 81.2705

I hope this helps.

Regards,
Dan McCormick

Giovanni Leoncini wrote:

> Hi All! ;)
> 
> 
> I'm trying to convert some eta netcdf files into
> vis5d. The AWIPS 211 eta files are on lambert
> conformal
> (http://www.ncep.noaa.gov/NCO/PMB/products/grids.html#GRID211)
> and in my code I'm passing, to v5dCreate, these
> parameter for the lambert projection:
> 
>       proj_args(1) = 25
>       proj_args(2) = 25
>       proj_args(3) = 53.00
>       proj_args(4) = 178.745
>       proj_args(5) = -95
>       proj_args(6) = 81.2705
> 
> the met fields are consistent with topography, but
> everything is rotated 90 deg clockwise, and I see
> hawaii north of california. Playing with these values
> (i.e. switching 3 and 4 or using 95 or 265 instead of
> -95) I'm only able to see different parts of the
> globe!
> 
> If I switch grid and colums I get the fields right,
> but the rockies still go from west to east!! 
> 
> any clue?
> 
> thanks a lot!
> 
> Giovanni 
> 
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