NoData in raster datasets

Cell values can be either positive or negative, integer, or floating point. Cells can also have a NoData value to represent the absence of data. Sometimes there are homogeneous areas in a raster dataset that the user does not want to display. These can include borders, backgrounds, or other data considered to not have valid values. Sometimes these are expressed as NoData values, although other times they may have real values.

When displaying rasters with NoData values, all renderers allow you to set the NoData value to a color or no color; however, the Stretched renderer allows you to identify a specific background value and display color or no color.

Learn about symbolizing values of NoData in raster datasets

When calculating the statistics for a raster dataset, you can choose to ignore any cells with NoData.

When performing operations on raster data containing NoData values, there are typically three ways that NoData is treated for each cell: NoData can be returned for the location no matter what; NoData is ignored, and a value is computed using any available values; or a value must be estimated, and NoData cannot be returned.

In ArcSDE and file geodatabases, if the original raster data contains NoData cells, a bit mask will be generated on the fly when loading the raster, and it will be stored in the database. The bit mask will be read, and NoData areas will be extracted at the time of retrieval.

When NoData is added to a geodatabase raster (not in ArcSDE) that already has a full-bit range (meaning that all the values in the bit range, for example, 0 to 255, are all represented by at least one cell), it will be promoted to the next higher bit depth. For example, a hillshade grid with cell values of 0 to 255, which then has NoData added to it, will be represented as unsigned 16 bit. The following table lists the rules for data type promotion:

Original file-based raster data type	Data type after loading to geodatabase
Unsigned 1-bit integer	Unsigned 4-bit integer
Unsigned 4-bit integer	Unsigned 8-bit integer
Unsigned 8-bit integer	Unsigned 16-bit integer
Signed 8-bit integer	Signed 16-bit integer
Unsigned 16-bit integer	Unsigned 32-bit integer
Signed 16-bit integer	Signed 32-bit integer
Unsigned 32-bit integer	Floating point 32-bit
Signed 32-bit integer	Floating point 32-bit

Rules for data type promotion

You can assign cell values in a raster dataset to be NoData using the Set Null tool. NoData values can also be assigned for a mosaic dataset using the Define Mosaic Dataset NoData tool. This tool will allow you to specify more than on NoData value.