Index: CRS.java
===================================================================
--- CRS.java	(revision 31482)
+++ CRS.java	(working copy)
@@ -16,6 +16,9 @@
  */
 package org.geotools.referencing;
 
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
 import java.util.Set;
 import java.util.Map;
 import java.util.HashSet;
@@ -35,8 +38,11 @@
 import org.opengis.referencing.crs.*;
 import org.opengis.referencing.datum.*;
 import org.opengis.referencing.operation.*;
+import org.opengis.referencing.cs.AxisDirection;
+import static org.opengis.referencing.cs.AxisDirection.*;
 import org.opengis.referencing.cs.CoordinateSystem;
 import org.opengis.referencing.cs.CoordinateSystemAxis;
+import org.opengis.referencing.cs.EllipsoidalCS;
 import org.opengis.referencing.operation.CoordinateOperation;
 import org.opengis.referencing.operation.CoordinateOperationFactory;
 import org.opengis.referencing.operation.MathTransform;
@@ -57,6 +63,8 @@
 import org.geotools.geometry.GeneralDirectPosition;
 import org.geotools.metadata.iso.citation.Citations;
 import org.geotools.metadata.iso.extent.GeographicBoundingBoxImpl;
+import org.geotools.referencing.crs.DefaultGeographicCRS;
+import org.geotools.referencing.cs.DefaultEllipsoidalCS;
 import org.geotools.referencing.factory.AbstractAuthorityFactory;
 import org.geotools.referencing.factory.IdentifiedObjectFinder;
 import org.geotools.referencing.operation.projection.MapProjection;
@@ -597,6 +605,31 @@
                 }
             }
         }
+        if(crs instanceof DefaultGeographicCRS && crs.getCoordinateSystem().getDimension() > 2) {
+            DefaultGeographicCRS originalCRS = (DefaultGeographicCRS) crs;
+            EllipsoidalCS originalCS = originalCRS.getCoordinateSystem();
+            
+            // extract the horizontal axis using a list of known horizontal directions
+            List<CoordinateSystemAxis> flatAxis = new ArrayList<CoordinateSystemAxis>();
+            Set<AxisDirection> flatDirections = new HashSet<AxisDirection>(
+                    Arrays.asList(NORTH, NORTH_EAST, NORTH_NORTH_EAST, NORTH_NORTH_WEST, NORTH_WEST, 
+                                  SOUTH, SOUTH_EAST, SOUTH_WEST, SOUTH_SOUTH_EAST, SOUTH_SOUTH_WEST, 
+                                  EAST, EAST_NORTH_EAST, EAST_SOUTH_EAST, 
+                                  WEST_NORTH_WEST, WEST_SOUTH_WEST));
+            for (int i = 0; i < originalCS.getDimension(); i++) {
+                CoordinateSystemAxis axis = originalCS.getAxis(i);
+                if(flatDirections.contains(axis.getDirection()))
+                    flatAxis.add(axis);
+            }
+            
+            // build the derivative CS and CRS... not sure what to make of the original properties...
+            if(flatAxis.size() != 2)
+                throw new IllegalArgumentException("Cannot extract flat component, there are " 
+                        + flatAxis.size() + " axis recognized as 'flat', expected 2");
+            EllipsoidalCS flatCS = null;
+            flatCS = new DefaultEllipsoidalCS(originalCS.getName().getCode() + "_2d", flatAxis.get(0), flatAxis.get(1));
+            return new DefaultGeographicCRS(originalCRS.getName().getCode() + "_2d", originalCRS.getDatum(), flatCS);
+        }
         return null;
     }