com.graphhopper.reader.dem

Class EdgeElevationSmoothing

java.lang.Object

com.graphhopper.reader.dem.EdgeElevationSmoothing

public class EdgeElevationSmoothing
extends Object

The ElevationData is read from rectangular tiles. Especially when going along a cliff, valley, or pass, it can happen that a small part of the road contains incorrect elevation data. This is because the elevation data is coarse and sometimes contains errors.

Author:

Robin Boldt

Constructor Summary

Constructors

Constructor and Description
EdgeElevationSmoothing()

Method Summary

Modifier and Type	Method and Description
static void	smoothMovingAverage(PointList geometry) This method smooths the elevation data of a PointList by calculating the average elevation over multiple points of that PointList.
static void	smoothRamer(PointList pointList, double maxElevationDelta) This method removes elevation fluctuations up to maxElevationDelta.

Methods inherited from class java.lang.Object

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

Constructor Detail

EdgeElevationSmoothing

public EdgeElevationSmoothing()

Method Detail

smoothMovingAverage

public static void smoothMovingAverage(PointList geometry)

This method smooths the elevation data of a PointList by calculating the average elevation over multiple points of that PointList.

smoothRamer

public static void smoothRamer(PointList pointList,
                               double maxElevationDelta)

This method removes elevation fluctuations up to maxElevationDelta. Compared to the smoothMovingAverage function this method has the advantage that the maximum slope of a PointList never increases (max(abs(slope_i))). The disadvantage is that the appearance might be still more spiky (at tower nodes) as a result when a bigger positive slope changes to a bigger negative slope.

The underlying algorithm is an adapted Ramer-Douglas-Peucker algorithm (see #2634) with a maximum elevation change and: 1. only elevation changes are considered and any lat,lon difference is ignored 2. instead of removing the point the elevation will be calculated from the average slope of the first and last point of the specified pointList