Grid-to-grid, grid-to-watershed, and similar geospatial transforms can very efficiently be realized by sparse matrix technology. Such transforms are particularly useful for the grid cell to/from watershed mappings needed for coupling watershed-based hydrological models with grid-cell based meteorological models. We have used these transforms for coupling the TOPLATS hydrological model with both the MM5 meteorological model and the NEXRAD Stage IV precipitation analyses, and for various other model couplings. We describe the advantages of this technique, as compared with other techniques, which frequently are purely grid-based.