tailieunhanh - Báo cáo khoa học: "Polyhedral representation of crown shape. A geometric tool for growth modelling"

Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp quốc tế đề tài:"Polyhedral representation of crown shape. A geometric tool for growth modelling. | Ann Sci For 1995 52 297-306 Elsevier INRA 297 Original article Polyhedral representation of crown shape. A geometric tool for growth modelling c Cluzeau 1 JL Dupouey 2 B Courbaud 3 INRA unite croissance production et qualité des bois 54280 Champenoux 2 INRA unite d ecophysiologie forestiere 54280 Champenoux 3 CEMAGREF division protection contre les erosions BP 76 38402 Saint-Martin-d Heres cedex France Received 14 March 1994 accepted 17 January 1995 Summary Tree or stand growth modelling often needs an explicit representation of crown shape. This is necessary for crown volume or external surface calculations or light penetration modelling. Many different representations have been used for this purpose. In this paper we explore the use of the polyhedral convex hull of the crown as a type of boundary representation. We present an application of this representation for the calculation of geometrical characteristics of common ash trees Fraxinus excelsiorL . Crown projection area calculated with the convex hull is closely related to the measured value. Moreover a strong relation exists between the basal area of the most external tree rings and the convex hull volume or surface area which indirectly validates the polyhedral representations. This relation however is no stronger than exists with the simpler crown projection surface area measurement. The convex hull is intermediate in terms of computation costs and efficiency between classical geometric shapes and more elaborate computer graphic representations. It is a simple and versatile tool for modelling purposes. crown shape representation computational geometry crown volume convex hull I pipe model Fraxinus excelsior L Resume Representation polyédrique de la forme du houppier. Un outil géométrique pour la modélisation de la croissance. La modélisation de la croissance des arbres OU des peuplements fait souvent appel à une representation géométrique du houppier. Cela est nécessaire pour par exemple les calculs de .