The Gridded Population of the World, Version 4 (GPWv4): Data Quality Indicators consist of three data layers created to provide additional information about the quality of input population data and to provide context for the population count and density grids. The water mask distinguishes between pixels that are completely water and/or ice (Total Water Pixels) and pixels that also contain land (Partial Water Pixels). The data context grid categorizes pixels with estimated zero population based on information provided in the census documents, such as areas that are part of a national park, areas that have no households, etc. The Mean Administrative Unit Area grid measures the mean unit size in square kilometers. The mean unit size grid provides a quantitative surface that indicates the size of the input unit(s) from which population count and density grids are derived.