jwo.landserf.process
Class FlowThread

java.lang.Object
  java.lang.Thread
      jwo.landserf.process.LSThread
          jwo.landserf.process.FlowThread

All Implemented Interfaces:

Runnable, JWInterruptionListener

public class FlowThread
extends LSThread

Creates a raster containing flow magnitudes. This can be used to detect drainage networks by selecting values above a given threshold.

Version:

2.3, 17th December, 2008.

Author:

Jo Wood

Nested Class Summary

Nested classes/interfaces inherited from class java.lang.Thread

Thread.State, Thread.UncaughtExceptionHandler

Field Summary

Fields inherited from class java.lang.Thread

MAX_PRIORITY, MIN_PRIORITY, NORM_PRIORITY

Constructor Summary

FlowThread(GISFrame gisFrame, int flowThreshold, float sampleRate)
Processes the primary raster to create the flow accumulation surface and possible flow vectors.

Method Summary

void	doProcessing() Performs the flow accumulation calculation.
RasterMap	getFlowAccumulation() Retrieves the newly created flow accumulation surface.

Methods inherited from class jwo.landserf.process.LSThread

checkStoppedThread, interruptionRequested, resetTimer, run, setErrorMessage, setFinalMessage, setMessage

Methods inherited from class java.lang.Thread

activeCount, checkAccess, countStackFrames, currentThread, destroy, dumpStack, enumerate, getAllStackTraces, getContextClassLoader, getDefaultUncaughtExceptionHandler, getId, getName, getPriority, getStackTrace, getState, getThreadGroup, getUncaughtExceptionHandler, holdsLock, interrupt, interrupted, isAlive, isDaemon, isInterrupted, join, join, join, resume, setContextClassLoader, setDaemon, setDefaultUncaughtExceptionHandler, setName, setPriority, setUncaughtExceptionHandler, sleep, sleep, start, stop, stop, suspend, toString, yield

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

FlowThread

public FlowThread(GISFrame gisFrame,
                  int flowThreshold,
                  float sampleRate)

Processes the primary raster to create the flow accumulation surface and possible flow vectors. Density of flow vectors can be controlled with sampleRate which randomly samples locations to be included as flow vectors and flowThreshold which sets the minimum flow accumulation required before a flow vector is drawn. Note that flowThreshold and sampleRate have no effect on the flow accumulation raster produced by this process. If sampleRate <= 0, no flow vectors are created.

Parameters:

flowThreshold - Minimum number of cells of flow accumulation to define a flow vector.

sampleRate - Proportion of cells to be sampled when calculating flow vectors (between 0 and 1).

gisFrame - GISFrame holding raster to process.

Method Detail

doProcessing

public void doProcessing()

Performs the flow accumulation calculation. This method uses the 'rolling ball' method suggested by Lea (1992) and uses non-raster flow positioning. This ensures that raster artifacts are minimised in the flow accumulation values. Flow does not accumulate across flat areas. The flow accumulation raster can be retrieved directly via this class's getFlowAccumulation() method, or by calling gisFrame.getRaster2();.

Note that this method will be called automatically if this is run as a threaded process (e.g. myFlowThread.start()). Alternatively it can be called directly as a non-threaded process.

Specified by:

doProcessing in class LSThread

See Also:

GISFrame

getFlowAccumulation

public RasterMap getFlowAccumulation()

Retrieves the newly created flow accumulation surface.

Returns:

New flow accumulation surface, or null if process yet to take place.