What does a zero in the population density grid mean? What does No Data mean?

The Water Mask and Data Context layers is the Data Quality Indicators data set provide helpful information regarding pixels labelled ‘0’ or ‘NoData’ in any of the population count or density rasters.

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). Inland pixels with values of ‘NoData’ in the population count and density rasters belong to Total Water Pixels.

The Data Context raster explains pixels with  ‘0’ population estimate in the population count and density rasters, based on information included in the census documents. Pixels are categorized into eight categories as shown in the table below.
Data Context Value Data Context Category
0 Not applicable
201 Park or protected area
202 Military district, airport zone, or other infrastructure
203 Not enumerated or not reported in census
204 No households
205 Uninhabited
206 Population not gridded
207 Missing age and/or sex data
Pixels in categories 201-204 were explicitly identified as such in the census documentation or boundaries.

Pixels in category 205 (‘Uninhabited’) belong to units where the reported total population in the census was ‘0’, but no further information was provide. A pixel categorized as ‘Uninhabited’ may therefore be uninhabited because it is a national park or a military district; however, due to the large number of units in GPWv4, we were unable to further research each unit to explain why the population count was ‘0’.
 
Pixels categorized as 206 (‘Population not gridded’) belong to administrative units where the data could not be gridded due to a lack of information or data integration issues. The units are currently being researched and will be updated in future releases if possible.

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