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Abstract:  Experimental results were studied to determine the relationships between positioning precision of a differential global positioning system (DGPS) and forest type, antenna height, and season, and to clarify the relationship between sampling number and the convergence of positioning precision. Observation was carried out for 24 h. Mean circular area probability (CEP95) was 2.80 m for deciduous broadleaved trees, and 4.99 m for conifers. The mean CEP95 taken at 7 m height (3.14 m) was higher than that at 1 m height (3.92 m) at all sites. The mean CEP95 taken during the defoliation season (2.65 m) was slightly better than during the foliation season (2.96 m). There were significant differences between forest types (P < 0.001) and antenna heights (P < 0.05). Positioning precision was not noticeably improved if the sampling number was around ten or less. A sampling number of 100–1000 or more is required before substantial improvements can be expected. As long as high positioning precision is not required, it is acceptable to use 2D & 3D modes and relatively few samples to take measurements.

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Amorphous film of NdDyFeCo alloy has been investigated for high performance magneto-optical disk. Studies on magneto-optic effect and magnetic properties found that a square of hysteresis loop and a coercivity of (Nd13Dy87)30(Fe84Co16)70were significantly improved, and large Kerr-rotation of 0.4 degree and Curie temperature of 150°C were obtained. Dynamic characteristics have revealed that magneto-optical disk of (Nd13Dy87)30(Fe84Co16)70film on polycarbonate substrate(5.25''-diam. with track pitch of 1.6µm) had high C/N ratio of 58dB and 49 dB at 2MHz and 5MHz, respectively. This media also enabled to write data with a high sensitive power of 6.25 mW with a rotation speed of 1800 rpm at radius of 60 mm where should correspond to a rotation speed of 3600 rpm at radius of 30 mm. (Nd13Dy87)30(Fe84Co16)70film promises the high data transfer rate recording of 10 Mbps for 5.25''-diam. is possible with high sensitivity under a recording power of 10 mW.