16 Sep 15:16 2014

### (residual) variograms and trend adjustment

Tim Richter-Heitmann <trichter <at> uni-bremen.de>

2014-09-16 13:16:27 GMT

2014-09-16 13:16:27 GMT

Hi! I just had a talk with a reviewer of my thesis. He strongly criticized the way i was interpreting variograms without previous trend adjustment. In fact, i am following the route in "Applied Spatial Data Analysis with R", chapter 8. On page 218, i think its stated the basic assumption of the variogram is that the variance of the random function Z is solely based on the separation distances. However, it was said that variograms should only display the residuals of Z (y=mx+b+e), never the complete term. I first should identify non-spatial trends in the data. I find this very difficult without knowing the autocorrelation of a dataset. So, the real question is, what comes first: Autocorrelation or pairwise correlations of observations? Starting with page 230 of the same book, there is a tutorial for residual variogramming, but i think this assumes that i already know the functions i want to test, or? How would you deal with this remark? Thanks, Tim