org.opentripplanner.profile

Class IsochroneGenerator

java.lang.Object

org.opentripplanner.profile.IsochroneGenerator

public abstract class IsochroneGenerator
extends Object

This class contains a couple of utility methods for making Isochrones when all you have is a PointSet and times to reach that PointSet. Eventually we may want to just define a standard grid PointSet for each study area in such a way that all streets within each grid cell contribute to its travel time value, then use that grid directly when making isolines. This would allow us to drop the separate grid accumulation step. The reason why we need this functionality is that we are now producing travel time stats directly for pointsets as targets of a repeated RAPTOR search, without saving accompanying travel time values for the street vertices along the way.

Field Summary

Fields

Modifier and Type	Field and Description
static double	GRID_SIZE_METERS
static double	WALK_DISTANCE_GRID_SIZE_RATIO

Constructor Summary

Constructors

Constructor and Description
IsochroneGenerator()

Method Summary

Modifier and Type	Method and Description
static List<IsochroneData>	getIsochronesAccumulative(ZSampleGrid<SampleGridRenderer.WTWD> grid, int spacingMinutes, int cutoffMinutes, int nMax) Make isochrones from a grid.
static ZSampleGrid	makeGrid(PointSet pointSet, int[] times, double walkSpeed) Make a ZSampleGrid from a PointSet and a parallel array of travel times for that PointSet.

Methods inherited from class java.lang.Object

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

Field Detail

GRID_SIZE_METERS

public static final double GRID_SIZE_METERS

See Also:

Constant Field Values

WALK_DISTANCE_GRID_SIZE_RATIO

public static final double WALK_DISTANCE_GRID_SIZE_RATIO

See Also:

Constant Field Values

Constructor Detail

IsochroneGenerator

public IsochroneGenerator()

Method Detail

makeGrid

public static ZSampleGrid makeGrid(PointSet pointSet,
                                   int[] times,
                                   double walkSpeed)

Make a ZSampleGrid from a PointSet and a parallel array of travel times for that PointSet. Those times could come from a ResultSetWithTimes or directly from a PropagatedTimesStore, which has one such array for each of min, avg, and max travel time over the departure time window it represents. If your PointSet is dense enough (e.g. every block in a city) then this should yield a decent surface and isochrones. FIXME code duplication, this is ripped off from TimeSurface and should probably replace the version there as it is more generic.

Parameters:

walkSpeed - the walk speed in meters per second

Returns:

a grid suitable for making isochrones, based on an arbitrary PointSet and times to reach all those points.

getIsochronesAccumulative

public static List<IsochroneData> getIsochronesAccumulative(ZSampleGrid<SampleGridRenderer.WTWD> grid,
                                                            int spacingMinutes,
                                                            int cutoffMinutes,
                                                            int nMax)

Make isochrones from a grid. This more general function should probably be reused by SurfaceResource. FIXME code duplication: function ripped off from SurfaceResource

Parameters:

spacingMinutes - the number of minutes between isochrones

Returns:

a list of evenly-spaced isochrones