Removing nodata values seemed like a good idea when doing a sort(), but this created some bugs (sometimes it is still valuable to know that y=nodata after sorting). This is now an optional behavior. The interpolated grids are now buffered in Meteo2DInterpolator. The grid buffering code has been cleaned up and backported to BufferedIOHandler. The spatial interpolations specific points (for virtual stations, etc) has been moved to Meteo2DInterpolator in order to make IOManager smaller and more focused on general data flow handling.