Hi there, I was wondering if by the way the isotropic bivariate function works in the mgcv package, one can use highly correlated coordinates (given the shape of the study area) without worrying about the potential problems of correlation between explanatory variables, i.e., does s(LON, LAT) deal with that by considering their combined effect? Although this sounds more like a statistical question, I think this question may also relate to how mgcv fits this function and thus may interest other readers. Thanks, Luciano [[alternative HTML version deleted]]