D-Infinity Distance Up
(c) 2010 by David G. Tarboton
This tool calculates the distance from each grid
cell up to the ridge cells along the reverse D-infinity flow directions.
Ridge cells are defined to be grid cells that have no contribution from
grid cells further upslope. Given the convergence of multiple flow paths
at any grid cell, any given grid cell can have multiple upslope ridge cells.
There are three statictical methods that this tool can use: maximum distance,
minimum distance and waited flow average over these flow paths. A variant
on the above is to consider only grid cells that contribute flow with a
proportion greater than a user specified threshold (t) to be considered
as upslope of any given grid cell. Setting t=0.5 would result in only one
flow path from any grid cell and would give the result equivalent to a D8
flow model, rather than D-infinity flow model, where flow is proportioned
between two downslope grid cells. Finally there are several different
optional paths that can be measured: the total straight line path (Pythagoras),
the horizontal component of the straight line path, the vertical component
of the straight line path, or the total surface flow path.
Parameters
- Number of Processes
Integer
- The number of stripes that the domain will be divided into and the
number of MPI parallel processes that will be spawned to evaluate each
of the stripes.
- D-Infinity Flow Direction Grid
Raster Grid
- A grid giving flow direction by the D-infinity method. Flow direction
is measured in radians, counter clockwise from east. This can be created
by the tool "D-Infinity Flow Directions".
- Pit Filled Elevation Grid
Raster Grid
- This input is a grid of elevation values. As a general rule, it is
recommended that you use a grid of elevation values that have had the
pits removed for this input. Pits are generally taken to be artifacts
that interfere with the analysis of flow across them. This grid can be
obtained as the output of the "Pit Remove" tool, in which case
it contains elevation values where the pits have been filled to the
point where they just drain.
- Slope Grid
Raster Grid
- This input is a grid of slope values. This is measured as drop/distance
and it is most often obtained as the output of the "D-Infinity
Flow Directions" tool.
- Statistical Method
Choise
- Statistical method used to calculate the distance down to the stream.
In the D-Infinity flow model, the outflow from each grid cell is
proportioned between two downslope grid cells. Therefore, the distance
from any grid cell to a stream is not uniquely defined. Flow that
originates at a particular grid cell may enter the stream at a number
of cells. The distance to the stream may be defined as the longest (maximum),
shortest (minimum) or weighted average of the distance down to the stream.
Default is Average.
- Distance Method
Choise
- Distance method used to calculate the distance down to the stream.
One of several ways of measuring distance may be selected: the total
straight line path (Pythagoras), the horizontal component of the straight
line path (horizontal), the vertical component of the straight line path
(vertical), or the total surface flow path (surface). Default is
Horizontal.
- Proportion Threshold
Double
- The proportion threshold parameter where only grid cells that
contribute flow with a proportion greater than this user specified
threshold (t) is considered to be upslope of any given grid cell.
Setting t=0.5 would result in only one flow path from any grid cell
and would give the result equivalent to a D8 flow model, rather than
D-Infinity flow model, where flow is proportioned between two downslope
grid cells. Default 0.5.
- Check for Edge Contamination
Boolean
- A flag that determines whether the tool should check for edge
contamination. This is defined as the possibility that a value may be
underestimated due to grid cells outside of the domain not being counted.
Default True.
Outputs
- D-Infinity Distance Up
Raster Grid
- Creates a grid containing the distances up to the ridge calculated
using the D-Infinity flow model and the statistical and path methods
chosen.