【摘要】 <正> 为了测定单株立木材积,普雷斯勒提出了望高法。其优点是简便易行,缺点是望点较高,通视较差,观测困难,且实际误差较大。希费尔提出了胸高形率法,琼森提出了绝对形率法。它们的优点是精度高,缺点是测定中央直径较麻烦。受上述方法的启示,根据干形特点,我们提出了形点法。用林分速测镜即可简便容易地测出较精确的立木材积。一、形点法的测树原理和方法 （一）基本原理令胸径为D,树高为h,胸高（1.3m）以上树干某点直径为aD（0<α<1）,干顶到aD点的干长为h₁,aD到D点的干长为h₂。按孔兹干曲线式y²=px^r有更多还原

【Abstract】 The from reference point is fixed on the position that diameter of the upper stem is equal to 0.5^1/2 times the diameter at breast height. According to this, the following conclusions are derived: the comprehensive form-exponent of the stem above breast height.It has been proved in practice that the average system error is -0.44% and standard error is 5.24% by comparing the volume obtained from form reference point method, namely ,with that from theseetional measurement.更多还原