GeoWorld December 2012

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Bringing Travel and Terrain Directions into Line Characterizing directional movement is needed in backcountry emergency BEYONDMAPPING N response, and it���s crucial in effective ot long ago, a short series of ���Beyond Mapping��� columns addressed ���Backcountry 911,��� which considers on- and off-road travel for emergency response (see GeoWorld, July-September, 2010; ���Author���s Note 1,��� page 11). As identi���ed in the left portion of Figure 1, the analysis involves development of a ���stepped accumulation surface��� that ���rst considers on-road travel by assigning the minimum travel-time from headquarters to all road locations. As shown in the ���gure, the farthest-away location via truck travel is 26.5 minutes, occurring in the southeast BY JOSEPH BERRY corner of the project area. The next step considers disembarking anywhere along the road network and moving off-road by ATV. However, the ability to simulate different modes of travel isn���t available in most grid-based map-analysis toolsets. The algorithm requires the off-road movement to ���remember��� the travel time at each road location, and then start accumulating additional travel time as the new movement twists, turns and stops with respect to the relative and absolute barriers calibrated for ATV off-road travel (see ���Author���s Note 2���). timber-harvest planning, wild���re-propagation modeling, pipeline routing and myriad other practical applications. hiking into these locations. In a similar manner, the algorithm picks up the accumulated truck/ATV travel-time values and moves into the steep areas, respecting the hiking dif���culty under adverse terrain conditions. Note the large increases in travel time in these hard-to-reach areas. The farthest-away location via combined truck, ATV and hiking is 96.0 minutes, also occurring in the project area���s central portion. A traditional accumulation surface (one single step) identi���es the minimum travel time from a starting location to all other locations considering ���constant��� de���nitions of the relative and absolute Adding It Up Joseph Berry is a principal in Berry & Associates, consultants in GIS technology. He can be reached via e-mail at 10 The middle-left inset in Figure 1 shows the accumulated travel-time for on-road truck and off-road ATV travel, where the intervening terrain conditions act like ���speed limits��� (relative barriers). Also, ATV travel is completely restricted by open water and very steep slopes (absolute barriers). The result of the processing assigns the minimum total travel time to all accessible locations, comprising about 85 percent of the project area. The farthest-away location via combined truck and ATV travel is 52.1 minutes, occurring in the project area���s central portion. The remaining 15 percent is too steep for ATV travel and necessitates G E O W O R L D / D E C E M B E R 2 O 1 2 ���Figure 1. A backcountry emergency-response surface identifies the travel time of the ���best path��� to all locations via a combination of truck, ATV and hiking travel.

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