This study focuses on "the distance parameter" that is indispensable component of a spatial interaction model on forest operation activites. Therefore theoretical approaches were discussed for the area distribution of the nearest-access distance from the individual stands within a certain bounded area to the nearest road in a forest road network. In the first, respecting complex boundaries of harvesting units, the probability distribution function of the nearest-access distance was obtained. The parameter z and the coefficient of curvature k derived from this function was shown to be some characterized geographical distance distribution-curves and geographical accessibility points to points. Also, we defined the index F_s to evaluate the distance reflecting the spatial autocorrelation and to take into account both the behavioral and configurational components. The index F_s is given by F_s=(l-p+q)/2, where p is an area ratio of shorter distance than the 1/3 of the maximum of distance and q is an area ratio of longer than the 2/3 of it in the concerned area. By the index F_s, we compared the different types of timber harvesting unit boundaries with forest road nets. Consequently, it could classify the technical difficulties of mechanized harvesting operations for tracts of either regular or irregular shape. In addition, we confirmed that the road net arrangement-index (f-value) being generalized the characteristies of forest roads system was closely concerned with the parameter z or k. That is, f is related to k by the equation f=1+2|k_t|.

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The purpose of this study was to clarify the optimum leg structure for semi-legged machine and make it possible to construct a small semi-legged machine with a small engine and hydraulic capacity which is useful for silvicultural operations. For this purpose, two different leg structures for the walking action of a semi-legged machine were compared in terms of drive torque and energy consumed. One of the leg structures was a knuckle boom type and the other was a pendulum type. The results on the knuckle boom type legs showed that as far as forward motion was concerned, the machine was efficient in climbing and going down gentle slopes. With regard to climbing middle to steep slopes the machine was found to be efficient in backward motion. This showed that the usual operation with existing semi-legged machines was a suitable one. The synchronous gait was very efficient on steep terrain. This result encouraged us to develop a new semi-legged machine which could walk in synchronous gait. Comparing the two pendulum type legs, the one with longer walking link consumed less energy though it needed more torque to be driven. This result indicates that the pendulum type leg has the potential for a faster moving speed, because the moving speed of the one with longer walking link was higher than the other in this study. Higher speed was an important point in developing the new machine, and this type of leg is a possible solution.

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To use processors practically, it is important to know about not only the performance but also its cost for machine maintenance. In this report, we traced the repairing histories of 13 processors operating in Miyazaki area, and calculated the repair fees of them also. We found that there are many easy cases included in whole repairing histories, so as a result of this study, we propose that machine user should be trained as a mechanic and repair small troubles by themselves for total cost reduction.

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The real-time differential global positioning system (DGPS) using the code system was tested in the forest, and the positioning ratios, positioning precision and factors that affect the positioning precision were analyzed. The invalid positioning ratio accounted for 23.1% of all data. The invalid positioning ratio was closely related to the three-dimensional(3D) positioning ratio in the 3D space (X,Y,Z). At a circular error probable of 95% (CEP_<95>), the positioning precision of measurements in the 2D space (X,Y) was 3.27 m and 4.00 m for the 3D and 2D positioning, respectively. The precision of the 3D positioning was estimated to be about 1 meter higher than that of the 2D positioning. The positioning precision of the measurement was 36% lower for the altitude (Z) than for (X,Y). Multiple regression analysis was used to find the factors that affected the positioning precision. The number of satellites and the position dilution of precision (PDOP) were chosen as the variables to decide the positioning precision. The multiple correlation coefficient was 0.423, and a weak correlation between the stand condition and the number of satellites was confirmed. It was found that the release of selective availability did not improve the positioning precision in the forest.

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We surveyed the inclination, surface roughness, and horizontal and vertical types of hillsides within equivalent areas to determine the best location for a forest road for light cableway yarding operations, using a small skidder-mounted yarder with a tower, or an excavator-mounted yarder. The objective of this study was to develop criteria for locating forest roads using a geographic information system that stores information about the terrain attributes of features by representing them as polygons in a spatial database. The geometric relationship of a selected polygon and two neighboring polygons defines the skyline profile involving the three polygons. Combinations of horizontal types (concave, equilibrium, or convex) represent the suitability of a setting and combinations of vertical types (basin, uniform, or cone-shaped) indicate the advantages of carrying out a yarding operation. These criteria also provide polygons useful in deciding where the head or tail spar is best placed, given several skyline profiles. Using this classification method, we were able to determine where the forest road was best located within the trial area.

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