Builds a structure of type "CellTree" (linked list of pixels).
handle_tree = CreateCellTree ( handle_fdr , outlet [, handle_weight] )
integer: handle on the flow direction grid to be used for constructing the topology
integer: ID of the outlet pixel (root of the tree), as returned by XY2rec
(optional) integer: raster containing the weight to use for each pixel in the tree. If no raster is specified, all pixels will have a unit weight.
output, integer: handle on the newly created tree structure
Builds a structure of type "CellTree" (linked list of pixels) having its root at an outlet cell. This structure makes it easier to search and sample among the pixels of the catchment.
Returns a handle on the object created.