OPERATIONS ON LOCAL NEIGHBORHOODS

# OPERATIONS ON LOCAL NEIGHBORHOODS - o slightly smooths the...

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OPERATIONS ON LOCAL NEIGHBORHOODS the value of a pixel on the new layer is determined by the local neighborhood of the pixel on the old layer Filtering a filter operates by moving a "window" across the entire raster o e.g. many windows are 3x3 cells the new value for the cell at the middle of the window is a weighted average of the values in the window by changing the weights we can produce two major effects: o smoothing (a "low pass" filter, removes or reduces local detail) o edge enhancement (a "high pass" filter, exaggerates local detail) weights should add to 1 example filters: 1. .11 .11 .11 .11 .11 .11 .11 .11 .11 o replaces each value by the simple unweighted average of it and its eight neighboring values o severely smooths the spatial variation on the layer 2. .05 .05 .05 .05 .60 .05 .05 .05 .05 o gives the pixel's old value 12 times the weight of its neighboring values
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Unformatted text preview: o slightly smooths the layer 3. -.1 -.1 -.1 -.1 1.8 -.1 -.1 -.1 -.1 o slightly enhances local detail by giving neighbors negative weights • filters can be useful in enhancing detail on images for input to GIS, or smoothing layers to expose general trends Slopes and aspects • if the values in a layer are elevations, we can compute the steepness of slopes by looking at the difference between a pixel's value and those of its adjacent neighbors • the direction of steepest slope, or the direction in which the surface is locally "facing", is called its aspect o aspect can be measured in degrees from North or by compass points - N, NE, E etc. • slope and aspect are useful in analyzing vegetation patterns, computing energy balances and modeling erosion or runoff o aspect determines the direction of runoff this can be used to sketch drainage paths for runoff...
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## This note was uploaded on 12/04/2011 for the course GEB 1011 taught by Professor Staff during the Fall '08 term at Broward College.

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