[gradsusr] Question on the use of PDEF for Lambert Conformal Conic mapping

Arlindo da Silva dasilva at alum.mit.edu
Mon Apr 25 21:59:19 EDT 2011


On Wed, Apr 20, 2011 at 5:02 PM, Huddleston, John <
Huddleston at cira.colostate.edu> wrote:

> Hi
>
>
>
> Attached are two images of the same data, one is a close up view and one is
> a view from space.
>
>
>
> The grid was made by taking the Lambert Conformal Conic grid in meters and
> projecting it to Mercator for display in Google earth.
>
>
>
> The sample data set was plotted with GrADS using PDEF to transform it again
> for display in Google earth.
>
>
>
> The view from space looks correct.
>
>
>
> The close up view shows the GrADS grid cells vertically up and down and
> they do not match the LCC grid.
>
>
>
> Is this the correct behavior for the plot?
>
>
>

I know that real cartographers uses an oblate model of the earth surface
(with 2 radius) to improve accuracy at regional scales, while grads uses a
spherical model with a single radius. Could you be reaching this limit where
the oblateness effects are important?

   Arlindo




John Huddleston
>
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-- 
Arlindo da Silva
dasilva at alum.mit.edu
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