private void computeTileOverlapPercentage( final int x0, final int y0, final int w, final int h, double[] overlapPercentages) throws Exception { final PixelPos pixPos = new PixelPos(); final GeoPos geoPos = new GeoPos(); final PosVector earthPoint = new PosVector(); final PosVector sensorPos = new PosVector(); double tileOverlapPercentageMax = -Double.MAX_VALUE; double tileOverlapPercentageMin = Double.MAX_VALUE; for (int y = y0; y < y0 + h; y += 20) { for (int x = x0; x < x0 + w; x += 20) { pixPos.setLocation(x, y); sourceGeoCoding.getGeoPos(pixPos, geoPos); final double alt = dem.getElevation(geoPos); GeoUtils.geo2xyzWGS84(geoPos.getLat(), geoPos.getLon(), alt, earthPoint); final double zeroDopplerTime = SARGeocoding.getEarthPointZeroDopplerTime( firstLineUTC, lineTimeInterval, wavelength, earthPoint, orbit.sensorPosition, orbit.sensorVelocity); if (zeroDopplerTime == SARGeocoding.NonValidZeroDopplerTime) { continue; } final double slantRange = SARGeocoding.computeSlantRange(zeroDopplerTime, orbit, earthPoint, sensorPos); final double zeroDopplerTimeWithoutBias = zeroDopplerTime + slantRange / Constants.lightSpeedInMetersPerDay; final int azimuthIndex = (int) ((zeroDopplerTimeWithoutBias - firstLineUTC) / lineTimeInterval + 0.5); double tileOverlapPercentage = (double) (azimuthIndex - y) / (double) tileSize; if (tileOverlapPercentage > tileOverlapPercentageMax) { tileOverlapPercentageMax = tileOverlapPercentage; } if (tileOverlapPercentage < tileOverlapPercentageMin) { tileOverlapPercentageMin = tileOverlapPercentage; } } } if (tileOverlapPercentageMin != Double.MAX_VALUE && tileOverlapPercentageMin < 0.0) { overlapPercentages[0] = tileOverlapPercentageMin - 0.5; } else { overlapPercentages[0] = 0.0; } if (tileOverlapPercentageMax != -Double.MAX_VALUE && tileOverlapPercentageMax > 0.0) { overlapPercentages[1] = tileOverlapPercentageMax + 0.5; } else { overlapPercentages[1] = 0.0; } }