| A new method for measuring single tree volume has been developed based on the theory of close-range photogrammetry and image measurement. The method shows much greater advantages than traditional metrical methods: more convenient for the measurement in field work with high metric precision. It initiates an entirely new methodology, i.e. digital and automatic means to measure single tree volume.The paper mainly reports the following work:(1) A single CCD digital camera is used as the input facility. Due to the limited visual field angle of the digital camera lens, a tree is shot with the camera section by section for its volume measuring without felling down the tree. First, photographic measurement is conducted in both horizontal and diagonal ways. Then follows image production work such as rectifying by projecting the images and patching up them. Consequently, the trunk image of the whole single tree is able to be obtained.The whole process of single tree metric trial is recorded in photograph form in order to reanalyze the measurement of the single tree and to study the growthcourse of trees afterwards.(2) For the measurement of single tree volume, we provide a direct linear transform equation of two-dimensional image, instead of three-dimensional analytic work so that the process is simplified and the computational work is remarkably reduced. With the image equation, the image coordinates can be transformed into object coordinates, and can be rectified the linear and nonlinear distortion created by digital camera.(3) For acclivitous photogrammetry, we work out the outside orientation parameter by deduction, namely the equation to calculate the gradient of a beam according to the same point respectively in two pictures and by the rectification of oblique photography. With the photographic metric method of normal pixel the tree-measure factors, such as trunk diameter at any height of a tree and a tree total height etc. can be obtained easily.(4) Based on the analysis of 944 felled down sample trees of 6 species, we provide the volume formulation estimated by normal form-factor and that can be collected from truck diameter at a height near ground. And the experience has indicated that the estimated precision can satisfy the requirement of production. The stem volume formulation can be used not only in the photograph measurement for stock volume, but also in the normal measurement for stock volume.(5) Based on the volume equation of single stem by subsection and the volume formulation estimated from normal form factors, we provide two technical paths to measure the volume of single stem volume with photograph.(6) In order to realize the automation of measurement, we have finished a great number of programming works with Delphi language.(7) It is an innovation in experimental means to use metric techniques of close-range photogrammetry and image to measure the stock volume. Among the studying demonstrated above, (2), (3), (4), and (5) are the innovations of this paper.
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