Modern Earth system models and global hydrological models require input data in the form of flow direction grids (rasters) with a relatively low resolution. Typical resolution for these models is about 0.5–1°. At high resolution, up to 1 km cell size, flow direction grids are usually generated from digital elevation models (DEMs), but for coarse-resolution grids, more specialized approaches need to be used. In this paper we review upscaling methods for flow direction grids, including grid-based flow tracing, catchment area aggregation and vector network processing. We also indicate methods that have been used to create publicly available datasets in global coverage (DRT and IHU), and provide links to these datasets. The paper also considers methods for estimating the result of flow direction generation on coarse-resolution grids, as well as the results of applying these estimates to existing methods. It is shown that the task of estimating the result requires further development, including the development of new estimation methods and comparative comparison of the most modern upscaling approaches.