From 673dbf659fd64fd799b0fb4640bc3d54795eb36f Mon Sep 17 00:00:00 2001
From: Luc Maisonobe <luc@orekit.org>
Date: Fri, 26 Sep 2014 11:32:06 +0200
Subject: [PATCH] Explained the index shift in the getXxxIndex methods.
---
.../java/org/orekit/rugged/raster/Tile.java | 12 +++++--
.../orekit/rugged/raster/SimpleTileTest.java | 36 +++++++++++++++++++
2 files changed, 46 insertions(+), 2 deletions(-)
diff --git a/core/src/main/java/org/orekit/rugged/raster/Tile.java b/core/src/main/java/org/orekit/rugged/raster/Tile.java
index d6abd003..eb91e9d2 100644
--- a/core/src/main/java/org/orekit/rugged/raster/Tile.java
+++ b/core/src/main/java/org/orekit/rugged/raster/Tile.java
@@ -128,13 +128,21 @@ public interface Tile extends UpdatableTile {
int getLongitudeColumns();
/** Get the latitude index of a point.
+ * <p>
+ * This method shift indices 1/2 pixel, so that
+ * the specified latitude is always between index and index+1.
+ * </p>
* @param latitude geodetic latitude
- * @return latirute index (it may lie outside of the tile!)
+ * @return latitude index (it may lie outside of the tile!)
*/
int getLatitudeIndex(double latitude);
/** Get the longitude index of a point.
- * @param longitude geodetic latitude
+ * <p>
+ * This method shift indices 1/2 pixel, so that
+ * the specified longitude is always between index and index+1.
+ * </p>
+ * @param longitude geodetic longitude
* @return longitude index (it may lie outside of the tile!)
*/
int getLongitudeIndex(double longitude);
diff --git a/core/src/test/java/org/orekit/rugged/raster/SimpleTileTest.java b/core/src/test/java/org/orekit/rugged/raster/SimpleTileTest.java
index a71c1ce1..ac0d4f97 100644
--- a/core/src/test/java/org/orekit/rugged/raster/SimpleTileTest.java
+++ b/core/src/test/java/org/orekit/rugged/raster/SimpleTileTest.java
@@ -115,6 +115,42 @@ public class SimpleTileTest {
checkOutOfBound( 50, 200, tile);
}
+ @Test
+ public void testIndexShift() throws RuggedException {
+
+ SimpleTile tile = new SimpleTileFactory().createTile();
+ tile.setGeometry(1.0, 2.0, 0.1, 0.2, 100, 200);
+ tile.setElevation(50, 100, 1000.0);
+ tile.tileUpdateCompleted();
+
+ // indices correspond to pixels centers
+ double latCenterColumn50 = tile.getLatitudeAtIndex(50);
+ double latCenterColumn51 = tile.getLatitudeAtIndex(51);
+ double lonCenterRow23 = tile.getLongitudeAtIndex(23);
+ double lonCenterRow24 = tile.getLongitudeAtIndex(24);
+
+ // getLatitudeIndex shift indices 1/2 pixel, so that
+ // the specified latitude is always between index and index+1
+ // so despite latWestColumn51 is very close to column 51 center,
+ // getLatitudeIndex should return 50
+ double latWestColumn51 = 0.001 * latCenterColumn50 + 0.999 * latCenterColumn51;
+ int retrievedLatIndex = tile.getLatitudeIndex(latWestColumn51);
+ Assert.assertEquals(50, retrievedLatIndex);
+ Assert.assertTrue(tile.getLatitudeAtIndex(retrievedLatIndex) < latWestColumn51);
+ Assert.assertTrue(latWestColumn51 < tile.getLatitudeAtIndex(retrievedLatIndex + 1));
+
+ // getLongitudeIndex shift indices 1/2 pixel, so that
+ // the specified longitude is always between index and index+1
+ // so despite lonSouthRow24 is very close to row 24 center,
+ // getLongitudeIndex should return 23
+ double lonSouthRow24 = 0.001 * lonCenterRow23 + 0.999 * lonCenterRow24;
+ int retrievedLonIndex = tile.getLongitudeIndex(lonSouthRow24);
+ Assert.assertEquals(23, retrievedLonIndex);
+ Assert.assertTrue(tile.getLongitudeAtIndex(retrievedLonIndex) < lonSouthRow24);
+ Assert.assertTrue(lonSouthRow24 < tile.getLongitudeAtIndex(retrievedLonIndex + 1));
+
+ }
+
private void checkOutOfBound(int i, int j, Tile tile) {
try {
tile.setElevation(i, j, 1000.0);
--
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