DBTR2013 - Water element - (CDA_GLI)

The water path for both natural and artificial watercourses is modelled by means of the centreline; each section of the centreline may be contained in a wet area or in any case in a riverbed and in this case it is defined as a physical centreline, or it may correspond to a sliding section that is not visible and in this case the centreline, where there is no doubt about the interpretation, corresponds to a line joining the point of end of visibility with the point of continuation and in this case the element of watercourse is of a fictitious type; Finally, it can be contained in a body of water, and in this case it is qualified as a virtual centreline.天然与人工河道的水体路径均以中心线（centreline）进行建模。中心线的各分段可分为以下三类情形：其一，该分段位于湿地区域或河床范围内，此时该中心线被定义为实体中心线（physical centreline）；其二，该分段对应不可见的滑动区段，若不存在解释歧义，则此类中心线为连接可见终止点与延续点的线段，此时对应的河道单元属于假想类型（fictitious type）；其三，该分段位于水体内部，此时该中心线被归类为虚拟中心线（virtual centreline）。