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Hi Dominik,<br>
<br>
Well, I was not exactly thinking in IDW, but more suggesting a DA scheme in which the observational error is explicitly taken into account. Anyway, about the exponential decay, in case you want to have a look, I referred to the Barnes scheme, which sometimes
called as "the Cressman analysis with an exponential decay". You may find a matlab code, e.g., at:<br>
<br>
<a href="http://www.nceo.ac.uk/cressman_scheme.php" target="_blank">http://www.nceo.ac.uk/cressman_scheme.php</a><br>
<br>
An some description at:<br>
<br>
<a href="http://www.atmos.millersville.edu/~lead/Obs_Data_Assimilation.html" target="_blank">http://www.atmos.millersville.edu/~lead/Obs_Data_Assimilation.html</a><br>
<br>
<br>
Regards,<br>
Javier<br>
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<div style="direction: ltr;" id="divRpF650125"><font color="#000000" face="Tahoma" size="2"><b>From:</b> Dominik Schneider [Dominik.Schneider@Colorado.EDU]<br>
<b>Sent:</b> 16 June 2014 15:43<br>
<b>To:</b> Javier Garcia-Pintado<br>
<b>Cc:</b> r-sig-Geo@r-project.org<br>
<b>Subject:</b> Re: [R-sig-Geo] cressman analysis<br>
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<div>Hi Javier -<br>
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I was thinking of using a cressman in place of an IDW scheme for interpolating. The reason would be because you can optimize the Radius of influence which has some physical meaning as opposed to optimizing the power in IDW.
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Where does the exponential decay fit into the equation?<br>
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Thanks!<br>
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<div>Dominik Schneider</div>
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<div>o 303.735.6296 | c 518.956.3978 </div>
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<br>
<div class="gmail_quote">On Fri, Jun 13, 2014 at 10:45 PM, Javier Garcia-Pintado <span dir="ltr">
<<a href="mailto:j.garcia-pintado@reading.ac.uk" target="_blank">j.garcia-pintado@reading.ac.uk</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex; border-left:1px #ccc solid; padding-left:1ex">
Hi Dominik,<br>
<br>
a) It won't take you more than a few of lines to code the Cressman analysis in R. You just need to decide what metric to use for the weighting function [e.g. a distance-based exponential decay?]<br>
<br>
b) Are you sure you want to use a Cressman analysis? It certainly is not the state-of-the-art in Data Assimilation<br>
<br>
<br>
Regards,<br>
Javier<br>
<br>
<br>
________________________________________<br>
From: <a href="mailto:r-sig-geo-bounces@r-project.org" target="_blank">r-sig-geo-bounces@r-project.org</a> [<a href="mailto:r-sig-geo-bounces@r-project.org" target="_blank">r-sig-geo-bounces@r-project.org</a>] on behalf of Dominik Schneider [<a href="mailto:Dominik.Schneider@colorado.edu" target="_blank">Dominik.Schneider@colorado.edu</a>]<br>
Sent: 13 June 2014 23:49<br>
To: <a href="mailto:r-sig-Geo@r-project.org" target="_blank">r-sig-Geo@r-project.org</a><br>
Subject: [R-sig-Geo] cressman analysis<br>
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Are there any implementations in R of the Cressman interpolation?<br>
<a href="https://nsidc.org/data/docs/daac/nsidc0033_arctic_water_vapor/cressman_equations.html" target="_blank">https://nsidc.org/data/docs/daac/nsidc0033_arctic_water_vapor/cressman_equations.html</a><br>
I haven't found anything via rseek or google.<br>
Thanks Dominik<br>
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