Summary
Creates an indicator grid (1,0) of upward curved grid cells according to the Peuker and Douglas algorithm.
With this tool, the DEM is first smoothed by a kernel with weights at the center, sides, and diagonals. The Peuker and Douglas (1975) method (also explained in Band, 1986), is then used to identify upwardly curving grid cells. This technique flags the entire grid, then examines in a single pass each quadrant of 4 grid cells, and unflags the highest. The remaining flagged cells are deemed 'upwardly curved', and when viewed, resemble a channel network. This proto-channel network generally lacks connectivity and requires thinning, issues that were discussed in detail by Band (1986).
Band, L. E., (1986), "Topographic partition of watersheds with digital elevation models," Water Resources Research, 22(1): 15-24.
Peuker, T. K. and D. H. Douglas, (1975), "Detection of surface-specific points by local parallel processing of discrete terrain elevation data," Comput. Graphics Image Process., 4: 375-387.
Usage
Command Prompt Syntax:
mpiexec -n <number of processes> PeukerDouglas
-fel <felfile>
-ss <ssfile>
-par 0.4 0.1 0.05
Parameters:
- felfile: File name for float grid of elevations (input)
- ssfile: File name for short indicator grid of upward curved grid cells, by Peuker and Douglas
- par: float array of parameters used to smooth DEM, p[0] being center weight, p[1] side weight, p[2] being diagonal weight
Syntax
PeukerDouglas (Input_Elevation_Grid, Center_Smoothing_Weight, Side_Smoothing_Weight, Diagonal_Smoothing_Weight, Input_Number_of_Processes, Output_Stream_Source_Grid)
| Parameter | Explanation | Data Type |
|---|---|---|
| Input_Elevation_Grid |
Dialog Reference A grid of elevation values. This is usually the output of the "Pit Remove" tool, in which case it is elevations with pits removed. There is no python reference for this parameter. |
Raster Layer |
| Center_Smoothing_Weight |
Dialog Reference The center weight parameter used by a kernel to smooth the DEM before the tool identifies upwardly curved grid cells. There is no python reference for this parameter. |
Double |
| Side_Smoothing_Weight |
Dialog Reference The side weight parameter used by a kernel to smooth the DEM before the tool identifies upwardly curved grid cells. There is no python reference for this parameter. |
Double |
| Diagonal_Smoothing_Weight |
Dialog Reference The diagonal weight parameter used by a kernel to smooth the DEM before the tool identifies upwardly curved grid cells. There is no python reference for this parameter. |
Double |
| Input_Number_of_Processes |
Dialog Reference 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. There is no python reference for this parameter. |
Long |
| Output_Stream_Source_Grid |
Dialog Reference An indicator grid (1,0) of upward curved grid cells according to the Peuker and Douglas algorithm, and if viewed, resembles a channel network. This proto-channel network generally lacks connectivity and requires thinning, issues that were discussed in detail by Band (1986). There is no python reference for this parameter. |
Raster Dataset |
Code Samples
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