Smoothing Filters - MapInfo_Pro_Advanced - 2023

The types of smoothing filters in MapInfo Pro Advanced include:

• Averaging filters - Averaging filter is a low-pass filter. In this method, each value of the grid cell is replaced by the average value of the filter neighborhood, including the central value. Averaging filter kernel can be of size 3x3, 5x5, or 7x7. While a 3x3 kernel will sufficiently smooth most datasets, you can use larger kernels like 5x5 or 7x7 for more comprehensive smoothing. Averaging filters are also used to enhance the sharpness of an image or improve the appearance of the edges. A typical averaging 3x3 filter will look like:

  				1	1	1
  				1	1	1
  				1	1	1
  			

  The averaging filters available in MapInfo Pro Advanced are:

  1. 3x3 Average filter
  2. 3x3 Diagonal filter
  3. 5x5 Average filter
  4. 7x7 Average filter
  5. 9x9 Average filter
• Gaussian filters - Gaussian filters remove high frequency noise. The degree of smoothing is usually determined by the standard deviation of the filter kernel. In this filter method, the output will contain a weighted average of each cell in the filter neighborhood, with the average weighted more towards the central node. Gaussian filters smoothens edges more than averaging filters do. In many cases, Gaussian filters are used as a pre-processing step to enhancement filters such as Laplacian or Sobel. A typical Gaussian 3x3 filter with a standard deviation of 0.39 will look like:

  				1	4	1
  				4	12	4
  				1	4	1
  			

  The Gaussian filters available in MapInfo Pro Advanced are:

  1. 3x3 Gaussian, Standard Deviation = 0.391
  2. 5x5 Gaussian, Standard Deviation = 0.625
  3. 5x5 Gaussian, Standard Deviation = 1.0
  4. 9x9 Gaussian, Standard Deviation = 1.0
  5. 11x11 Gaussian, Standard Deviation = 1.6