X-Git-Url: http://gitweb.fperrin.net/?p=GpsPrune.git;a=blobdiff_plain;f=src%2Ftim%2Fprune%2Fdata%2FGradientCalculator.java;fp=src%2Ftim%2Fprune%2Fdata%2FGradientCalculator.java;h=04846e7914f8a4c133a0c00a18a4d2ba0c14c0bf;hp=0000000000000000000000000000000000000000;hb=ce6f2161b8596f7018d6a76bff79bc9e571f35fd;hpb=2d8cb72e84d5cc1089ce77baf1e34ea3ea2f8465

diff --git a/src/tim/prune/data/GradientCalculator.java b/src/tim/prune/data/GradientCalculator.java
new file mode 100644
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--- /dev/null
+++ b/src/tim/prune/data/GradientCalculator.java
@@ -0,0 +1,56 @@
+package tim.prune.data;
+
+/**
+ * Abstract class to hold static calculation functions
+ * for gradient (like glide slope)
+ */
+public abstract class GradientCalculator
+{
+	/**
+	 * Calculate the gradient value of the track at the specified index
+	 * @param inTrack track object
+	 * @param inIndex index of point to calculate gradient for
+	 * @param inValue object in which to place result of calculation
+	 */
+	public static void calculateGradient(Track inTrack, int inIndex, SpeedValue inValue)
+	{
+		if (inValue != null)
+		{
+			inValue.setInvalid();
+		}
+		if (inTrack == null || inIndex < 0 || inValue == null)
+		{
+			System.err.println("Cannot calculate gradient for index " + inIndex);
+			return;
+		}
+
+		// If no altitude or it's a waypoint then no gradient either
+		DataPoint point = inTrack.getPoint(inIndex);
+		if (point == null || !point.hasAltitude() || point.isWaypoint()) {
+			return;
+		}
+
+		// If the point has horizontal and vertical speeds already then just use those
+		if (point.hasHSpeed() && point.hasVSpeed()) {
+			inValue.setValue(point.getVSpeed().getValueInMetresPerSec() / point.getHSpeed().getValueInMetresPerSec());
+		}
+		else if (!point.getSegmentStart())
+		{
+			// Use the previous track point and the next track point
+			DataPoint p = inTrack.getPreviousTrackPoint(inIndex-1);
+			DataPoint q = inTrack.getNextTrackPoint(inIndex+1);
+			if (p != null && q != null && !q.getSegmentStart()
+				&& p.hasAltitude() && q.hasAltitude())
+			{
+				final double horizRads = DataPoint.calculateRadiansBetween(p, point) +
+					DataPoint.calculateRadiansBetween(point, q);
+				final double horizDist = Distance.convertRadiansToDistance(horizRads, UnitSetLibrary.UNITS_METRES);
+				final double heightDiff = q.getAltitude().getMetricValue() - p.getAltitude().getMetricValue();
+				// Get gradient in radians
+				final double gradient = Math.atan2(heightDiff, horizDist);
+				inValue.setValue(gradient);
+			}
+		}
+		// otherwise, just leave value as invalid
+	}
+}