diff --git a/vtm/src/org/oscim/map/Viewport.java b/vtm/src/org/oscim/map/Viewport.java
index 8e54b603..35e8fe29 100644
--- a/vtm/src/org/oscim/map/Viewport.java
+++ b/vtm/src/org/oscim/map/Viewport.java
@@ -80,6 +80,9 @@ public class Viewport {
     protected final float[] mu = new float[4];
     protected final float[] mViewCoords = new float[8];
 
+    /**
+     * Height and width in pixels
+     */
     protected float mHeight, mWidth;
 
     public static final float VIEW_DISTANCE = 3.0f;
diff --git a/vtm/src/org/oscim/renderer/GLViewport.java b/vtm/src/org/oscim/renderer/GLViewport.java
index 44f8bf62..1b1495d0 100644
--- a/vtm/src/org/oscim/renderer/GLViewport.java
+++ b/vtm/src/org/oscim/renderer/GLViewport.java
@@ -128,10 +128,16 @@ public class GLViewport extends Viewport {
         getMapExtents(plane, 0);
     }
 
+    /**
+     * @return width in pixels
+     */
     public float getWidth() {
         return mWidth;
     }
 
+    /**
+     * @return height in pixels
+     */
     public float getHeight() {
         return mHeight;
     }