[R-sig-Geo] Variogram modeling

[Edzer Pebesma]

On 02/18/2014 06:11 PM, Moshood Agba Bakare wrote:
> Dear All,
> In my yield data, I have longitude and latitude as spherical coordinates
> which are converted into projected coordinates - easting and northing for
> variogram modelling, yield as attribute variable, and elevation.
> I fitted my empirical variogram as
> empvar<-variogram(yield~1,canmod.sp,cutoff=600,width=3, cressie=TRUE).
> In some documents I come across, some fitted the model using easting and
> northing as covariate to yield as
> yield ~easting+northing rather than yield ~1.
> which one do you advise me to use yield ~easting+northing or yield ~1.

If there is a strong spatial trend, general advice is to work on the
residuals (~easting+northing), and use the same equation in the kriging
step (universal or regression kriging).

You could try both, if the difference is small, I'd suggest to not
detrend (ie., use ~1)

-- 
Edzer Pebesma
Institute for Geoinformatics (ifgi), University of Münster
Heisenbergstraße 2, 48149 Münster, Germany. Phone: +49 251
83 33081 http://ifgi.uni-muenster.de GPG key ID 0xAC227795

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