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GeoWorld August 2011

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Figure 2. A procedure identifies pLZs with sufficient surrounding canopy clearance. cells are contiguous. First, locations with a simple binary sum of 3 or 4 are assigned 1; else = 0. A binary-progression weighted window (i.e., 1, 2, 4, 8, 16, 32, 64, 128) is used to generate a weighted focal sum of the neighboring cells. The weighted sum results in a unique value for all possible configurations of the clear surrounding cells (see Figure 2's lower portion). For example, the only configuration that results in a sum of 7 is the binary-progression weights of 1 + 2 + 4 indicating contiguous cells N, NE, E. The weighted binary-progression sums indicating contiguous cells then are reclassified to 1; 0 = else. Finally, the minimum value for the "Greater than 4 Clear" and "3 or 4 Clear" maps is taken, resulting in 1 for locations having sufficient contiguous canopy- clearance cells; else = 0. Stay Effective The top portion of Figure 3 outlines the procedure for evaluating sufficient negative slope by determin- ing the difference between the minimum surrounding elevation and each pLZ elevation. If the difference is greater than 10 feet, a map value of 1 is assigned; else = 0. The final step multiplies the binary maps of Potential LZ, Canopy Clearance and Minimum Negative Slope. The result is a map of the Effective LZs as 1 * 1 * 1 = 1 for locations meeting all three criteria. In the operational model, the negative-slope requirement was dropped as the client felt it was of marginal importance. Next month's column will describe the analysis approaches for identifying Figure 3. Procedures identify pLZs with sufficient negative slope (top) and combine all three considerations (bottom). AUGUST 2O11 / WWW . GEOPLA CE . COM 11 ground-response areas, helicopter rappelling zones and the translation of all three response modes into travel-time estimates for comparison. Author's Notes: For more information on Fire Program Solutions and their wildfire projects, contact Don Carlton at DCARLTON1@aol.com. For more discussion of back-country access and response applications, see the online book, Beyond Modeling III, Topic 29, Spatial Modeling in Natural Resources, at www.innovativegis.com/Basis/MapAnalysis/Default.htm.

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