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Diversity Options...
(b) |
Diversity Options is where you specify the sample size of the area around each pixel. The diversity Grid number is the radius of the grid. So, a grid of 5 (the default value) translates into a grid of 11x11 or a sample of 121 pixels around every pixel in the area being computed. The largest gird possible is a grid of 15 which equals a sample of 31x31 or 961 pixels around each pixel. Note: the time to compute diversity is controlled entirely by the sampling regime you choose. Thus, a grid of 15 will take three times as long to compute as a grid of 5. There is no rule-of-thumb regarding what grid to deploy. Much is dependent on the spatial resolution of the original image being processed. Suffice it to say that small grids allows the visualization of diversity at small scale, and large grids show diversity at large scale. In the case of SPOT image, a grid of 1 (9 pixels) is just under one acre, a grid of 5 (121 pixels) is 12.1 acres and a grid of 15 (961 pixels) is 96.1 acres. I recommend computing and displaying diversity in a test area of a few inches square for several grids before processing an entire image. Display Range (L), is preset to outline polygons of all pixels of or in excess of 75% of their maximum possible diversity. Change this display range to examine any portion of this range. In image (a) the range displayed is 70%-100%, in image (b), the range displayed is 0%-30% and in image (c), the range is 50%-60%. (c) 
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Diversity Options |
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