三维前方交会法测量树高及其精度分析

Measurement and precision analysis of tree height by 3D forward intersection.

为了解决森林调查中因地形起伏不能通过皮尺或者视距法获得测站与目标树的水平距离,而导致不能通过一般三角测量的办法来测量树高的问题,该文将测量高程的前方交会法应用到测树上来获得树高数据.前方交会法的内容为两台仪器与目标树构成一个三角形,测量两台仪器中心的斜距和三个夹角,利用正弦定理推算目标树与一台仪器的水平距离,然后再测得树顶和树根两处的天顶距,利用三角测量获得树高.经纬仪和罗盘仪是森林调查中常用的工具,通过对该模型的精度分析和实验发现经纬仪采用此方法可以控制误差在5%以内,满足林业上的测量要求,而罗盘仪采用此方法误差范围超过5%,不能满足要求.此方法可以配合经纬仪进行树高测量.

Because of hypsography,the horizontal distance between the station and the target tree cannot be measured easily by tape or stadia in forest survey to calculate the tree height with triangular surveying.In order to solve this matter,the authors applied the forward intersection to survey tree height.The content of the forward intersection is to construct a triangle with two stations and target tree,measure the distances between the two stations and three angles,then get the distance between one station and the target tree by law of sines,finally the perpendicular direction angle is measured,and the tree height is calculated.Theodolite and compass are used broadly in forest survey.Precision analysis and experiments demonstrated that the relative precision of tree height was less than 5% with theodolite and overrun 5% with compass.The precision of theodolite can satisfy the application in forestry.A conclusion is drawn that forward intersection can be taken in measuring tree height with theodolite.