Inerpolating/extrapolating to fill missing data

[Arlindo da Silva]

On Thu, Sep 11, 2008 at 6:05 PM, Chris Leather <chris at a-connect.co.uk>wrote:

>  Hi,
>
>
>
> I'm trying to create charts from NOAA data and have almost cracked it BUT
> as you can see from the attached graphic, I'm ending up with a jagged
> 'shadow' around the coasts where the data stops.
>
>
>
> I figure what I need to do is somehow extrapolate the data using something
> like nearest neighbour algorithm.
>
>
What exactly are yo trying to accomplish? 1) Are you trying to have values
over land or 2) have the boundary of data/no-data following a smoother
coastline? Extrapolating data over land is very controversial, and in the
few cases when this is done (for example, for sea level pressure) this is
extrapolation is done from "above" by reducing the fields to a certain
standard pressure level. Now, having the data following a smoother coastline
is not exactly a trivial endeavor.

   Arlindo

--
Arlindo da Silva
dasilva at alum.mit.edu
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