[R-sig-Geo] Inverse distance weighting in 3 dimension using gstat package

[Frede Aakmann Tøgersen]

Hi Edzer

Thank you very much, your observation was really helpful. So it was an error on my side :-( Nice that new eyes catch such errors so quickly.

The z values in the cfd data frame (data from computational fluid dynamics calculation of wind plow patterns) is height above sea level plus the height of wind turbine tower (here 95 m). The z values in the mastCFD data frame for meterological masts is just height above sea level. So this will cause a dip in the interpolated values at mast positions. The values of aspZ is calculated from the z values. So adjusting the z values in mastCFD to that of z values in cfd solves the problem. See the nice plot at https://www.dropbox.com/s/q30m3edjyhbuugj/Ainterp_more_correct.png?dl=0.  

Again, thanks.

Yours sincerely / Med venlig hilsen


Frede Aakmann Tøgersen
Specialist, M.Sc., Ph.D.
Plant Performance & Modeling

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> -----Original Message-----
> From: R-sig-Geo [mailto:r-sig-geo-bounces at r-project.org] On Behalf Of
> Edzer Pebesma
> Sent: 7. januar 2015 09:31
> To: r-sig-geo at r-project.org
> Subject: Re: [R-sig-Geo] Inverse distance weighting in 3 dimension using
> gstat package
> 
> 3D interpolation projected on irregular 2D is always somewhat tricky to
> comprehend. After looking at the plot, I tried:
> 
> > library(sp)
> > pts = SpatialPoints(mastCFD[c("x", "y")])
> > grd = cfd
> > gridded(grd) = ~x+y
> > over(pts,grd)
>          z   vxymag     aspZ  Ainterp
> 1 877.9992 11.70016 75491.32 4.700857
> 2 902.3500 13.44538 77585.03 4.669962
> > mastCFD
>        x       y      z                           mast     A     aspZ
> 1 586987 1566348 788.82 MASTBenakanahalli1_78_0m___Ch2 4.766 67823.60
> 2 591592 1562582 808.44 MASTBenakanahalli2_78_0m___Ch2 4.622 69510.55
> 
> and wondered why mastCFD$z is different from the cfd$z values at the
> corresponding locations.
> 
> 
> On 01/07/2015 07:31 AM, Frede Aakmann Tøgersen wrote:
> > Hi
> >
> > Anyone got experiences with interpolation in 3 dimensions?
> >
> > I am doing some inverse distance interpolation in 3 dimensions using the

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