GIS 311 Lecture Notes - Lecture 3: Map Algebra
30 Nov 2017
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Identify the key operators used in map algebra: explain the difference between map algebra operations, local operation on one pixel at a time, for all pixels. Compute a new raster layer where it is a function of one or more cell values at the same location on the input layers. Typically, combines single-theme grids, frequencies, statistical analysis, change detections, boolean (1/0 operators/t-f), and conversion of units: focal group of pixels at a time (neighborhood operation), produces an average. Output value of cell and influence of its neighbors, for kernel/smoothing/moving window. Most commonly a 3x3 window: zonal operation on a zone (common group of pixels). Function of the cell values within a zone containing the cell. Needs a zone layer that defines the zones. The value layer contains raw input values across extent of raster. Zones are anything that has the same value across the extent, and does not have to be adjacent.
