MODELLING PRODUCTIVITY IN EXTRACTION OPERATIONS BY SIMULATIONS BASED ON GNSS DOCUMENTED DATA: AN EXAMPLE FROM SKIDDING TEAK WOOD IN THAILAND
In Thailand, teak harvesting always includes skidding of tree length logs from landing to log yard for further processing. When terrain does not set limitations for the machines to be used, skidding is carried out by farm tractors. In this study, data was collected from 10 work cycles of teak extraction to simulate productivity of farm tractors. The GNSS data as speed and locations was used to extract operational distances and time consumption, as well as to support productivity simulation. For this, detailed measurements were done on the extracted stems to collect their diameters and lengths. For approximately six stems per load, the mean load size was 1.723 m3. The study found that mean productivity was 17.4 m3/h during the survey, where the mean extraction distance was 217 m. Our simulation presents productivity diagrams in relation to skidding distance. By simulation, we detected that reducing the full operational speed by 1 km/h, would decrease productivity 1 m3/h, when the extraction distance is less than 100 m. Another observation was that even small reductions of load sizes have a remarkable effect on productivity in short distances. Until large scale studies are to be done to evaluate the productivity in relation to variations in load size and extraction distance, the results shown herein could stand as a basis for productivity assessments.