This research examined damage to a residual stand from a selective cutting in a Hiba (Thujopsis dolabrara) natural forest. The analysis was performed using GIS. As a result of full-length logging operations using the tractor system, the rate of damaged residual trees reached 22.5%, and almost half of the damaged trees were damaged fatally. The proportion of fatally damaged trees was a mere 2.6% for the rest of the Hiba stand volume. The damage ratio was not related to the size of the residual Hiba. The main types of injury were, in descending order, fallen trees, broken stems, and naked sapwood, accounting for 89.7% of the total. The damage was mainly caused by felling and skidding. The results confirmed that the rate of damage and the distance from a road network, a stem and a felling tree were correlated with spatial spaces in the area, with the damage ratio decreasing as the distance increased. A hazard map of the logging damage was made from these results.

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The cone index of the forest floor, and possible factors affecting it, including precipitation and soil moisture content, were measured in a clear-cut area for nine months from May 1998 to January 1999, and again in December 1999, to examine the effects of logging operations on forest soil hardness. The cone index of the forest soil in a timber yard used 5 years earlier remains high. The cone index of the forest floor after logging increased with decreasing soil moisture content due to soil dryness. The cone index of the forest soil remained between 2.0 to 3.0 kgf/cm^2. Performing logging operations during winter, when the soil moisture content is low, can reduce soil compaction. Forestry machines used during the rainy season should be designed to exert a ground contact pressure of less than 1.5kgf/cm^2.

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The success of forest regeneration activities is strongly influenced by seedling quality. Better quality seedlings tend to have higher survival and growth rates. A PC-based machine vision system, which uses a Charge-Coupled-Device (CCD) camera and digital image processing techniques, was developed to increase the efficiency and accuracy of data collection in measuring morphological properties of forest seedlings in order to get better seedlings. The system relies on indirect illumination and specified hook, which is to hang seedling. Tests were conducted with a prototype of the vision system to measure Korean pine (Pinus koraiensis) seedlings. Machine vision measurements of shoot height, stem diameter, and root volume were compared with manual measurements. In the case of shoot height and stem diameter, the results showed high correlation (r=0.993 and 0.929 calculated correlation coefficient, respectively) and high accuracy (6.14 and 0.34mm calculated standard error, respectively) between machine vision and manual measurements, but in the case of root volume factor, the correlation coefficient between the machine vision and manual measurement was not so good as 0.768. These results indicate the machine vision system is a useful tool for morphological measurement of tree seedlings and might have future applications in the automation of nursery grading.

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This study deals with the accuracy of GPS surveys in forest. Several factors affect the accuracy of GPS static positioning using carrier phase analysis. The degree of spatial openness without obstruction caused by tree canopies or slopes surrounding a survey station affects the station's ability to receive satellite signals; the position dilution of precision and changes in the epochs of satellites receivable may affect the survey results. This study consists of two series of observations, one of 1-hour surveys at 43 stations and another of 7-hour surveys at 15 stations. The logged data for the 7-hour surveys were separated into fourteen 30-minute data sets, nine 45-minute data sets, and seven 60-minute data sets as different trials. Baseline processing was used to produce a covariance matrix of accuracy. The second set of observations was used to calculate the distance between the baseline coordinates and the average coordinates calculated using the seven 60-minute data sets. It was found that the degree of openness without obstruction affected the accuracy of the survey. We estimated the 90% confidence limits using an exponential formula. Consequently, when surveying in forest, the degree of spatial openness without obstruction should exceed 80%. This guarantees that at least the amount of epochs logged is the same as 4 satellites receivable for all of the survey period and PDOP is less than 7 for at least 2/3 of the survey period. Difference in the length of the survey period did not have a clear effect on the average coordinates, but shorter periods showed increased variance.

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For the purpose of using knuckle boom cranes, which are standard manipulators of forestry machines, for tasks besides handling and felling, locus and load control equipment for a knuckle boom crane has been developed. Functioning without a load-cell sensor, this control equipment interpolates the load value in the boom tip from position sensors and pressure gages installed in hydraulic cylinders of the knuckle boom crane. Load-cell sensors are not used because they are too expensive. Therefore, the load value in the tip is interpolated using equations of motion of the knuckle boom crane, and the measurement error is only 1kN or less at the speculation load value. In a control experiment using this speculation value, it was possible to manipulate the knuckle boom crane, while keeping the load error within 0.5kN and locus error within several cm. These errors are sufficiently small to use for forestry work. Therefore, load control of the knuckle boom crane is possible, even if a load-cell sensor is not used.

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