Spatial interpolation possibilities
On 12/03/2010 03:38 PM, Arnaud Mosnier wrote:
Dear GeoUseRs,
From the large number of methods that can be used to spatially interpolate
data, we tried several of them (Inverse Distance Weighted, Natural Neighbour, Spline, Kriging, Co-Kriging) on our dataset. We used ArcGIS to apply the first three and R for kriging and test possibilities of co-kriging. We do not have external independent data to test results of interpolations. The solution is probably to do a kind of cross-validation but doing it into ArcGIS seems difficult to implement. I know that I can do Inverse distance weighted interpolation in R but ... - Is it possible to do Natural Neighbour and Spline interpolation in R ? And if yes how ?
Hi Arnaud, Spline is possible, look at the Tps function from the fields package. I'm not sure on Natural Neighbor, but voronoi tessalations are available in R.
ArcGIS tools propose to consider "barriers" when using Inverse Distance Weighted and Spline tools. Thus, for example, interpolation occurring North from an island do not consider information located South of this island ... a quite important thing in our case. - I wondering if it is possible to do the same with gstat or another package ?
You could split up the dataset in two regions and interpolate them seperately. Finally, if you want to cross-validate, look at the compare.cv function from the automap package. It provides statistics and some spatial plots of the cross-validation residuals which I found very useful (I wrote them myself ;)). When cross-validating non-gstat interpolations you need to make sure that the output of the cross-validation is compatible (i.e. a SpatialPointsDataFrame with a few specific attributes). I have an example of how to do this with Tps, which can serve as inspiration. If you are interested I can send the code off list. Paul
Thanks for your help ! Arnaud [[alternative HTML version deleted]]
_______________________________________________ R-sig-Geo mailing list R-sig-Geo at r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-geo
Paul Hiemstra, MSc Department of Physical Geography Faculty of Geosciences University of Utrecht Heidelberglaan 2 P.O. Box 80.115 3508 TC Utrecht Phone: +3130 253 5773 http://intamap.geo.uu.nl/~paul http://nl.linkedin.com/pub/paul-hiemstra/20/30b/770 currently @ KNMI paul.hiemstra_AT_knmi.nl