Grapple skidder and stroke delimber-based harvesting systems produce approximately 80 of the annual timber in Maine. Productivity studies on such systems are time consuming and often interfere with a logging contractor's business. Computer simulations, such as agent-based modelling, represent one way to avoid interference with a logging business and to evaluate a variety of system configurations. We developed such a model to test four different operational scenarios to show whether it is possible toinfluence idle time, unit cost, and productivity of the system. The scenarios included a conventional skidding pattern, a modified skidding pattern assisted by an increase in operator communication and the use of Global Positioning System (GPS) and Geographic Information System (GIS), a change in delimbing behavior to decrease processing time, and the use of two grapple skidders to increase utilization of the delimber. The use of GPS- and GIS-aided operator communication did not drastically change percent idle time, productivity, or unit costs of the system. An analysis of annual cost savings showed that GPS- and GIS-aided communication between machine operators only marginally decreased the unit cost of production and in most cases resulted in an annual cost saving of less than $100. Using a second grapple skidder, however, resulted in annual cost savings of upwards of 880,000 based on skidding distance, bunch spacing, and removal intensity. Our conclusion is that logging contractors and land managers should investigate whether or not the use of two grapple skidders can lower their unit cost of production.
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