Dear Jeffrey,
thanks for your prompt reply and sorry for the double posting of this thread! I tried the Spline function and adjusted weight and number of points, but am ending up with really odd output values. My data should be in a range of 0 to 4.5, but the Spline output ranges in some cases from -400 to +800. This occurs for the regularized as well as the tension spline type and I'm not entirely sure why it happens. The data work fine with Kriging and the model output looks good, with a mean error close to zero (-0.001) and RMS standardized close to 1 (please correct if this interpretation is wrong).
I do not have a theoretical basis which provides a good reason to replicate the method used in Matlab in ArcGIS. I only assumed that linear interpolation is required as everyone, who I know is handling current flow data, is using it - basically a fairly bad reason. I had a few discussions with oeanographers today, asking why linear interpolation is so commonly used with current flow data. The general reply was: because it is simple and easy. So no deeper theory behind it. Accodingly I decided now to use kriging. My sampling area is only 6 km^2, which means that the difference might not have a huge effect either. Additionally the stats behind it support the model prediction, thus it is acceptable.
Would you agree with this?
Best regards,
Astrid