This tool can be used to extract channel networks from digital elevation models (DEMs). The Peucker and Douglas (1975) algorithm is one of the simplest and earliest algorithms for this purpose. Their 'valley recognition' method operates by passing a 2 x 2 roving window over a DEM and flagging the highest grid cell in each group of four. Once the window has passed over the entire DEM, channel grid cells are left unflagged. This method is best applied to DEMs that are relatively smooth and do not exhibit high levels of short-range roughness. As such, it may be desirable to use a smoothing filter before applying this tool.
This method of extracting valley networks results in line networks that can be wider than a single grid cell. As such, it is often desirable to thin the resulting network using a line-thinning algorithm. The option to perform line-thinning is provided by the tool as a post-processing step.
The following is an example of a Python script that uses this tool:
wd = pluginHost.getWorkingDirectory()
demFile = wd + "DEM.dep"
outputFile = wd + "output.dep"
lineThinning = "true"
args = [demFile, outputFile, lineThinning]
pluginHost.runPlugin("ExtractValleysPeuckerAndDouglas", args, False)
This is a Groovy script also using this tool:
def wd = pluginHost.getWorkingDirectory()
def demFile = wd + "DEM.dep"
def outputFile = wd + "output.dep"
def lineThinning = "true"
String[] args = [demFile, outputFile, lineThinning]
pluginHost.runPlugin("ExtractValleysPeuckerAndDouglas", args, false)