When NoData is added to a file-based raster 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. ![]() The bit mask will be read, and NoData areas will be extracted at the time of retrieval. In ArcSDE and file geodatabases, if the original raster data contains NoData cells, a bit mask will be generated when loading the raster, and it will be stored in the database. For example, -9999 is a common value for storing NoData. NoData is stored as a mask that is part of the raster dataset, or using a pixel value in the dataset that is not used as a valid value elsewhere in the dataset. A value must be estimated, and NoData cannot be returned.NoData is ignored, and a value is computed using any available values.NoData can be returned for the location no matter what.When performing operations on raster data containing NoData values, there are typically three ways that NoData is treated for each cell: When calculating the statistics for a raster dataset, you can choose to ignore any cells with NoData. Learn about symbolizing values of NoData in raster datasets ![]() The image on the left shows a NoData area with a black background, and the image on the right shows that same area using no color. 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. Sometimes these are expressed as NoData values, although other times they may have real values. These can include borders, backgrounds, or other data considered to not have valid values. Sometimes there are homogeneous areas in a raster dataset that the you do not want to display. Cells can also have a NoData value to represent the absence of data. Which is significantly less typing and you don't need to search all over your keyboard for the pipe (|) symbol to do a C style OR.Cell values can be either positive or negative, integer, or floating point. Which can get quite long winded, however for Integer rasters (not floating point) like classified rasters you can use the SQL in operator: Value in (3,5,7,9) so where the expression is true the output will be the input, where it's false it will be 0.įor individual values (for example 3,5,7,9) you can specify implicitly: Value = 3 || Value = 5 || Value = 7 || Value = 9 this is saying where the expression is true the output will be what's in the input the false raster or constant is 0. ![]() Note that the input conditional raster and input true raster or constant are the same value. Your SQL statement has the potential to be quite long unless you've got a suitable range for example: Value > 350 & Value < 360 || Value = 340 The tool you want to use is Con, although you can do it with Extract by Attributes Con gives you more control over the 'false' case. As you have reclassified this raster I'll assume that you have access to the Spatial Analyst extension, so will continue with instructions that require this extension.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |