[R-sig-Geo] R: Inverse distance weighting

[Clint Bowman]

Jiyoung,

Although there are R functions to do spatial interpolation, I'd advise
caution when working with air pollution data.  Be sure that topographic
and emission patterns are sufficiently smooth that you can do simple
spatial interpolation.

A technique which will likely produce better results where topographic
features are important or where the emissions are not spatially uniform is
to use a dispersion model to produce an estimate of the concentration over
the region of interest.  Now the dispersion model may not be completely
accurate, but it will reflect the spatial variation of the emission
sources quite accurately and should also do an adequate job of accounting
for the topography.

Now at each point where the concentration is measured, take the difference
between the observed and predicted concentrations.  Now spatially
interpolate that difference and apply it to the modeled values.  The US
EPA has a program, BenMAP, (Benefits MAPping) that can help with the
process.  Or you can use RSAGA as Alessandro suggested.

Clint

Clint Bowman			INTERNET:	clint at ecy.wa.gov
Air Dispersion Modeler		INTERNET:	clint at math.utah.edu
Air Quality Program		VOICE:		(360) 407-6815
Department of Ecology		FAX:		(360) 407-7534

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On Fri, 20 Mar 2009, Alessandro Montaghi wrote:

> Hey Jiyoung,
>
> I use RSAGA package to do interpolation with IDW. You need to install SAGA
> GIS and library(RSAGA).
>
> The command is
>
> rsaga.geoprocessor(lib="grid_gridding", module=0,....................
>
>
> I hope this is help you
>
> Ale
>
>
> -----Messaggio originale-----
> Da: r-sig-geo-bounces at stat.math.ethz.ch
> [mailto:r-sig-geo-bounces at stat.math.ethz.ch] Per conto di JY SON
> Inviato: venerdì 20 marzo 2009 18.24
> A: r-sig-geo at stat.math.ethz.ch
> Oggetto: [R-sig-Geo] Inverse distance weighting
>
> Dear everyone,
>
>
>
> I try to do spatial interpolation using R.
>
> I have air pollution monitoring data from 13 monitoring stations.
>
> I'd like to make estimates of unmeasured points using IDW (Inverse Distance
> Weighting) method.
>
> I have coordinates of monitoring station and unmeasured points.
>
> It would be highly appreciated if you let me know which function and library
> I can use to do the above.
>
>
>
> Best regards,
>
> Jiyoung
>
>
>
>
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>
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