Filter types

Standard deviation filters

 

For each group of pixels in the input map, a standard deviation filter calculates the standard deviation and assigns this value to the center pixel in the output map.

Standard deviation filters can be useful for radar images. The interpretation of radar images is often difficult: you can not rely on spectral values because of back scatter (return of the pulse sent by the radar). This often causes a lot of 'noise'. By using a standard deviation filter, you may be able to recognize some patterns.

The formula to calculate the standard deviation reads:

 

where:

xi

are the individual pixel values of the input map considered by the filter

is the mean of the pixel values considered by the filter

r

is the size of the filter in rows

c

is the size of the filter in columns

Standard standard deviation filters:

There is no standard standard deviation filter stored on disk.

User-defined standard deviation filters:

In the Filter dialog box as well as on the command line, you can define a standard deviation filter: specify the size of the filter. For more information and some examples, refer to User-defined standard deviation filters.

See also: