Development of Forest Survey Method by Combining GPS and Laser Ranging Instrument

1.利用全球定位系统和激光测距仪直接测量磁北偏差在进行森林测量时，通常使用三角测量点或其他授权点来确定点的地理坐标。但这样的点在林区分布稀少。如果该地区的磁北偏角是已知的，即使通过罗盘测量也很容易确定地理坐标。本文提出了一种利用GPS和激光测距仪直接测量磁北方位角的方法。本研究以位于北海道的东京大学森林和位于千叶的大学森林为研究对象。在北海道，我们发现该地区的磁北向偏移与据说的相差1度或更多。此外，我们还发现大学森林学院内部几乎有1度的差异。利用GPS和激光测距仪进行林分配置图制图的研究在千叶东京大学林的一块试验地上，对利用激光测距仪进行林分配置图制图的方法进行了检验。我们发现，LRI辅助映射是更容易，更快，更有效的比传统的方法。测量时间缩短了不到一半，而且只需要两个人进行测量。通过使用Excel和Lotus 1-2-3等电子表格型软件，测量数据的后处理也很容易。利用全球定位系统定位和该地区的磁北偏移（用上述方法测量），很容易在地理坐标上绘制林分布局坐标。这意味着我们可以很容易地确定森林中任何一点的地理坐标。森林地理信息系统的实施将需要这种信息作为基础数据。我们相信我们的方法将有助于实现这一目标。

1. Direct measurement of magnetic north declination using GPS and Laser Ranging InstrumentTo carry out a forest survey to identify geographic coordinates of the point, triangulation point or other authorized points are usually used. But such a points are sparsely allocated in forest area. If magnetic north declination of the area is known, it is easy to identify geographic coordinates even by the compass survey. In this research, we developed a direct measurement method of magnetic north declination using GPS and Laser Ranging Instrument (LRI). Tokyo University Forest in Hokkaido and University Forest in Chiba are selected as research field. In Hokkaido, we found magnetic north declination of the area is different for 1 degree or more then it is said. Also we found that there are almost 1 degree difference within the University Forest teritory.2. Study on stand disposition mapping method using GPS and Laser Ranging InstrumentExamination of stand disposition mapping method using LRI are carried out in a expermental plot of the Tokyo University Forest in Chiba. We found that LRI-aided mapping is much easier, faster and efficient then traditional method. Measuring time was reduced to less than half, and also only two person were needed for measurement. Post processing of measurement data is also easy by using spread-sheet-type software such as Excel and Lotus 1-2-3. Stand disposition coordinates are easily plotted on geographic coordinates, using GPS positioning and magnetic north declination of the area (measured by the method developed above). It means we can easily identify the geographic coordinates of any point in the forest. Implementation of forest GIS will require this kind of information as the basic data. We believe our method will contribute to such a purpose.