Handling collections of 2-dimensional grids (e.g. ZT grids from acoustic current profilers) is a straightforward extension of the techniques described under collections of profiles. If the time axes of the input grids are all identical, no additional work is needed beyond the techniques described there. If the time axes differ then follow the guidance given under Collections of Time Series, using intermediate variable definitions that reconcile the time axes into a single uniform axis before saving the input variables into a merged output file.