downstreamdist

downstreamdist

Distance to the first cell downstream

Result = downstreamdist(ldd)

ldd

spatial ldd

Result

spatial scalar

Options

--unittrue or --unitcell

--unittrue

distance is measured in true distance (default)

--unitcell

distance is measured in number of cell lengths

Operation

For each cell, assigns to Result the distance to the first cell downstream, where downstream cells are determined using the local drain directions on ldd. This distance is the length of one cell in case the local drain direction is to one of the right, left, top or bottom neighbouring cells or sqrt(2) multiplied by the length of one cell in case the local drain direction is to one of the 4 neighbouring cells in diagonal directions. In case a cell doesn’t have a downstream cell (i.e. a pit) a zero is assigned to Result.

Notes

A cell with a missing value on ldd is assigned a missing value on Result.

Group

This operation belongs to the group of Neighbourhood operators; local drain directions

See Also

lddmask

Examples

1. • pcrcalc

   binding

   Result = Result.map;

   Ldd2 = Ldd2.map;

   initial

   report Result = downstreamdist(Ldd2);

   
   

   • python

   Ldd2 = readmap(“Ldd2.map”)

   Result = downstreamdist(Ldd2)

   Result.map	Ldd2.map