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implemented "circular" search for non-NaN values in GRIB files

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Change-Id: I1216fd756aff24d7800924074d113ceb51e2a530
This commit is contained in:
Axel Uhl
2017-02-02 21:30:47 +01:00
parent 76ebba9735
commit 702082b334
1 changed files with 50 additions and 3 deletions
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java/com.sap.sailing.grib/src/com/sap/sailing/grib/impl/AbstractGribWindFieldImpl.java
+50 -3
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@@ -13,6 +13,7 @@ import com.sap.sailing.grib.GribWindField;
import com.sap.sse.common.Duration;
import com.sap.sse.common.TimePoint;
import com.sap.sse.common.TimeRange;
import com.sap.sse.common.Util.Pair;
import com.sap.sse.common.Util.Triple;
import com.sap.sse.common.impl.MillisecondsTimePoint;
import com.sap.sse.common.impl.TimeRangeImpl;
@@ -191,9 +192,55 @@ public abstract class AbstractGribWindFieldImpl implements GribWindField {
timeIndex = -1; // time index doesn't matter if no time dimension exists for the grid
responseTimePoint = getStartTime();
}
final Array arrayForTimePointBefore = grid.readDataSlice(timeIndex, /* z_index */ 0, xy[1], xy[0]);
final Position responsePosition = toPosition(coordinateSystem.getLatLon(xy[0], xy[1]));
return new Triple<Double, TimePoint, Position>((double) arrayForTimePointBefore.getFloat(0), responseTimePoint, responsePosition);
Pair<Double, Position> nearestNonNaNValueWithPosition = getNearestNonNaNValueWithPosition(
coordinateSystem, grid, timeIndex, /* zIndex */ 0, xy[1], xy[0], /* distance */ 0);
return new Triple<Double, TimePoint, Position>(nearestNonNaNValueWithPosition.getA(), responseTimePoint, nearestNonNaNValueWithPosition.getB());
}
/**
* Tries to find a non-{@code NaN} value starting at a given "distance" from a grid point. "Distance" here means the
* following: a grid point (x, y) has distance d from a grid point (a, b) if and only if {@code Math.abs(a-x)==d &&
* Math.abs(b-y)<=d || Math.abs(a-x)<=d && Math.abs(b-y)==d}. These points are intersected with the bounds as
* defined by the dimensions and then probed until a non-{@code NaN} value is found. The position for the grid point
* where such a value was found is then returned. If no such point is found with the exact distance, the next higher
* distance is probed recursively. If no such point exists within the bounds of the grid,
* {@code new Pair<>(NaN, null)} will be returned.
*/
private Pair<Double, Position> getNearestNonNaNValueWithPosition(GridCoordSystem coordinateSystem,
GridDatatype grid, int timeIndex, int zIndex, int yIndex, int xIndex, int distance) throws IOException {
final int minX = Math.max(0, xIndex-distance);
final int maxX = Math.min(grid.getXDimension().getLength()-1, xIndex+distance);
final int minY = Math.max(0, yIndex-distance);
final int maxY = Math.min(grid.getYDimension().getLength()-1, yIndex+distance);
if (minX>maxX || minY>maxY) { // empty range
return new Pair<>(Double.NaN, null);
}
for (int x=minX; x<=maxX; x++) {
for (int y = minY; y <= maxY; y += Math.max(1, maxY - minY)) { // scan upper and lower row; increment even if single-element range to trigger condition
final double valueAsFloat = getValue(grid, timeIndex, zIndex, x, y);
if (!Double.isNaN(valueAsFloat)) {
final Position responsePosition = toPosition(coordinateSystem.getLatLon(x, y));
return new Pair<>(valueAsFloat, responsePosition);
}
}
}
for (int y=minY+1; y<maxY; y++) {
for (int x = minX; x <= maxX; x += Math.max(1, maxX - minX)) { // scan left and right border without top/bottom elements
final double valueAsFloat = getValue(grid, timeIndex, zIndex, x, y);
if (!Double.isNaN(valueAsFloat)) {
final Position responsePosition = toPosition(coordinateSystem.getLatLon(x, y));
return new Pair<>(valueAsFloat, responsePosition);
}
}
}
// nothing found so far; tail-recurse for next greater distance
return getNearestNonNaNValueWithPosition(coordinateSystem, grid, timeIndex, zIndex, yIndex, xIndex, distance+1);
}
private double getValue(GridDatatype grid, int timeIndex, int zIndex, final int x, final int y) throws IOException {
final Array arrayForTimePointBefore = grid.readDataSlice(timeIndex, zIndex, y, x);
final double valueAsFloat = (double) arrayForTimePointBefore.getFloat(0);
return valueAsFloat;
}
protected Optional<String> getUnit(VariableDS variable) {