NoData in raster datasets
Last modified September 22, 2008
Print all topics in : "Properties of raster data"
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 geodatabase, 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 thru 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|