org.geotools.process.vector

Class HeatmapSurface

Object

HeatmapSurface

public class HeatmapSurface
extends Object

Computes a Heat Map surface from a set of irregular data points, each containing a positive height value. The nature of the surface is determined by a kernelRadius value, which indicates how far out each data points "spreads".

The Heatmap surface is computed as a grid (raster) of values representing the surface. For stability, the compute grid is expanded by the kernel radius on all four sides. This avoids "edge effects" from distorting the surface within the requested envelope.

The values in the output surface are normalized to lie in the range [0, 1].

Author:

Martin Davis, OpenGeo

Constructor Summary

Constructors

Constructor and Description
HeatmapSurface(int kernelRadius, Envelope srcEnv, int xSize, int ySize) Creates a new heatmap surface.

Method Summary

Modifier and Type	Method and Description
void	addPoint(double x, double y, double value) Adds a new data point to the surface.
float[][]	computeSurface() Computes a grid representing the heatmap surface.

Methods inherited from class Object

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

Constructor Detail

HeatmapSurface

public HeatmapSurface(int kernelRadius,
                      Envelope srcEnv,
                      int xSize,
                      int ySize)

Creates a new heatmap surface.

Parameters:

kernelRadius - the kernel radius, in grid units

srcEnv - the envelope defining the data space

xSize - the width of the output grid

ySize - the height of the output grid

Method Detail

addPoint

public void addPoint(double x,
                     double y,
                     double value)

Adds a new data point to the surface. Data points can be coincident.

Parameters:

x - the X ordinate of the point

y - the Y ordinate of the point

value - the data value of the point

computeSurface

public float[][] computeSurface()

Computes a grid representing the heatmap surface. The grid is structured as an XY matrix, with (0,0) being the bottom left corner of the data space

Returns:

a grid representing the surface