diff --git a/src/main/java/org/orekit/rugged/api/SensorPixelCrossing.java b/src/main/java/org/orekit/rugged/api/SensorPixelCrossing.java
index 8325b951a587df72d804e5f9f8933ffbbca7e38d..1c3f85c28dd5b07c99e161284e48e01a35eb971c 100644
--- a/src/main/java/org/orekit/rugged/api/SensorPixelCrossing.java
+++ b/src/main/java/org/orekit/rugged/api/SensorPixelCrossing.java
@@ -35,7 +35,7 @@ import org.orekit.time.AbsoluteDate;
 class SensorPixelCrossing {
 
     /** Margin before and after end pixels, in order to avoid search failures near boundaries. */
-    private final double MARGIN = 5.0;
+    private static final double MARGIN = 5.0;
 
     /** Line sensor. */
     private final LineSensor sensor;
diff --git a/src/main/java/org/orekit/rugged/raster/TilesCache.java b/src/main/java/org/orekit/rugged/raster/TilesCache.java
index 4606083a508296f6a8a254cbcc00a73ba7d5957b..901233080f9ce0f1e13c09df953ee3c44ecf0766 100644
--- a/src/main/java/org/orekit/rugged/raster/TilesCache.java
+++ b/src/main/java/org/orekit/rugged/raster/TilesCache.java
@@ -16,6 +16,7 @@
  */
 package org.orekit.rugged.raster;
 
+import java.io.Serializable;
 import java.lang.reflect.Array;
 import java.util.ArrayList;
 import java.util.Collections;
@@ -341,7 +342,10 @@ public class TilesCache<T extends Tile> {
     }
 
     /** Comparator for sorting with respect to latitude. */
-    private static class LatitudeComparator implements Comparator<LatitudeProvider> {
+    private static class LatitudeComparator implements Comparator<LatitudeProvider>, Serializable {
+
+        /** Serializable UID. */
+        private static final long serialVersionUID = 20141212L;
 
         /** {@inheritDoc} */
         @Override
@@ -352,7 +356,10 @@ public class TilesCache<T extends Tile> {
     }
 
     /** Comparator for sorting with respect to longitude. */
-    private static class LongitudeComparator implements Comparator<LongitudeProvider> {
+    private static class LongitudeComparator implements Comparator<LongitudeProvider>, Serializable {
+
+        /** Serializable UID. */
+        private static final long serialVersionUID = 20141212L;
 
         /** {@inheritDoc} */
         @Override
diff --git a/src/main/java/org/orekit/rugged/utils/NormalizedGeodeticPoint.java b/src/main/java/org/orekit/rugged/utils/NormalizedGeodeticPoint.java
index e60879a63b242383b287fe2bad2788b5a908a8a5..4f1813740b6fb68fa6d0ae8cfea9f16fbc40579d 100644
--- a/src/main/java/org/orekit/rugged/utils/NormalizedGeodeticPoint.java
+++ b/src/main/java/org/orekit/rugged/utils/NormalizedGeodeticPoint.java
@@ -55,4 +55,20 @@ public class NormalizedGeodeticPoint extends GeodeticPoint {
         return normalizedLongitude;
     }
 
+    /** {@inheritDoc} */
+    @Override
+    public boolean equals(final Object object) {
+        // we override the method just to make it clear that we INTENTIONALLY
+        // consider normalized point are just similar to regular points
+        return super.equals(object);
+    }
+
+    /** {@inheritDoc} */
+    @Override
+    public int hashCode() {
+        // we override the method just to make it clear that we INTENTIONALLY
+        // consider normalized point are just similar to regular points
+        return super.hashCode();
+    }
+
 }