# Changes between Version 4 and Version 5 of Processing/AplUserGuide

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Timestamp:
Feb 7, 2012 11:53:22 AM (8 years ago)
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• ## Processing/AplUserGuide

 v4 '''Nearest Neighbour''' Mapping with nearest neighbour searches the neighbourhood around the grid cell and finds the closest point to this from the IGM file. The corresponding value from the level-1 file is then used for this pixel. This option is selected using -interpolation nearest on the command line. Mapping with nearest neighbour searches the neighbourhood around the grid cell and finds the closest point to this from the IGM file. The corresponding value from the level-1 file is then used for this pixel. This option is selected using {{{-interpolation nearest}}} on the command line. '''Inverse Distance Weighted''' The inverse distance weighted algorithm first searches for, at most, the X nearest points within the maximum allowed search distance. The number X is specified from the command line in the -interpolation option. Then when these points have been found it calculates a weight for each point and applies this to the value of the data from the level-1 file. The weight for point i is  calculated as (distance^−2) / (Sum distance^−2) . This option is selected using -interpolation idw maxpoints where maxpoints is the maximum number of points you want to use. The inverse distance weighted algorithm first searches for, at most, the X nearest points within the maximum allowed search distance. The number X is specified from the command line in the -interpolation option. Then when these points have been found it calculates a weight for each point and applies this to the value of the data from the level-1 file. The weight for point i is  calculated as (distance^−2^) / (Sum (distance^−2^)) . This option is selected using {{{-interpolation idw maxpoints}}} where maxpoints is the maximum number of points you want to use. '''Bilinear''' where f(x) is the data value of cell x. Bilinear interpolation can be selected using -interpolation bilinear on the command line. Bilinear interpolation can be selected using {{{-interpolation bilinear}}} on the command line. === Example aplmap commands ===