tim/prune/data/GradientCalculator.java

   1 package tim.prune.data;
   2
   3 /**
   4  * Abstract class to hold static calculation functions
   5  * for gradient (like glide slope)
   6  */
   7 public abstract class GradientCalculator
   8 {
   9         /**
  10          * Calculate the gradient value of the track at the specified index
  11          * @param inTrack track object
  12          * @param inIndex index of point to calculate gradient for
  13          * @param inValue object in which to place result of calculation
  14          */
  15         public static void calculateGradient(Track inTrack, int inIndex, SpeedValue inValue)
  16         {
  17                 inValue.setInvalid();
  18                 if (inTrack == null || inIndex < 0 || inValue == null)
  19                 {
  20                         System.err.println("Cannot calculate gradient for index " + inIndex);
  21                         return;
  22                 }
  23
  24                 // If no altitude or it's a waypoint then no gradient either
  25                 DataPoint point = inTrack.getPoint(inIndex);
  26                 if (point == null || !point.hasAltitude() || point.isWaypoint()) {
  27                         return;
  28                 }
  29
  30                 // If the point has horizontal and vertical speeds already then just use those
  31                 if (point.hasHSpeed() && point.hasVSpeed()) {
  32                         inValue.setValue(point.getVSpeed().getValueInMetresPerSec() / point.getHSpeed().getValueInMetresPerSec());
  33                 }
  34                 else if (!point.getSegmentStart())
  35                 {
  36                         // Use the previous track point and the next track point
  37                         DataPoint p = inTrack.getPreviousTrackPoint(inIndex-1);
  38                         DataPoint q = inTrack.getNextTrackPoint(inIndex+1);
  39                         if (p != null && q != null && !q.getSegmentStart()
  40                                 && p.hasAltitude() && q.hasAltitude())
  41                         {
  42                                 final double horizRads = DataPoint.calculateRadiansBetween(p, point) +
  43                                         DataPoint.calculateRadiansBetween(point, q);
  44                                 final double horizDist = Distance.convertRadiansToDistance(horizRads, UnitSetLibrary.UNITS_METRES);
  45                                 final double heightDiff = q.getAltitude().getMetricValue() - p.getAltitude().getMetricValue();
  46                                 // Get gradient in radians
  47                                 final double gradient = Math.atan2(heightDiff, horizDist);
  48                                 inValue.setValue(gradient);
  49                         }
  50                 }
  51                 // otherwise, just leave value as invalid
  52         }
  53 }