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

[Huddleston, John]

Arlindo

Thank you for taking the time to review the results.

I did not know that GrADS uses a spherical model with a single radius like the NCEP sphere.

That puts a whole new light on the issue.

Let me do some additional research.

John

________________________________
From: gradsusr-bounces at gradsusr.org [gradsusr-bounces at gradsusr.org] On Behalf Of Arlindo da Silva [dasilva at alum.mit.edu]
Sent: Monday, April 25, 2011 7:59 PM
To: GrADS Users Forum
Subject: Re: [gradsusr] Question on the use of PDEF for Lambert Conformal Conic mapping

On Wed, Apr 20, 2011 at 5:02 PM, Huddleston, John <Huddleston at cira.colostate.edu<mailto: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<mailto:dasilva at alum.mit.edu>
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