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					</element>
					<element name="distance" type="gml:LengthType">
						<annotation>
							<documentation> distance is the distance at which the
							 offset curve is generated from the basis curve. In 2D systems, positive distances
							 are to be to the left of the basis curve, and the negative distances are to be to the 
							 right of the basis curve. 
      							</documentation>
						</annotation>
					</element>
					<element name="refDirection" type="gml:VectorType" minOccurs="0">
						<annotation>
							<documentation> refDistance is used to define the vector
       direction of the offset curve from the basis curve. It can
       be omitted in the 2D case, where the distance can be 
       positive or negative. In that case, distance defines left
       side (positive distance) or right side (negative distance)
       with respect to the tangent to the basis curve.

       In 3D the basis curve shall have a well defined tangent 
       direction for every point. The offset curve at any point 
       in 3D, the basis curve shall have a well-defined tangent
       direction for every point. The offset curve at any point
       (parameter) on the basis curve c is in the direction
       -   -   -         -               
       s = v x t  where  v = c.refDirection()  
       and
       -
       t = c.tangent()
                                                    -
       For the offset direction to be well-defined, v shall not
       on any point of the curve be in the same, or opposite, 
       direction as
       - 
       t.

       The default value of the refDirection shall be the local
       co-ordinate axis vector for elevation, which indicates up for
       the curve in a geographic sense.

       NOTE! If the refDirection is the positive tangent to the
       local elevation axis ("points upward"), then the offset
       vector points to the left of the curve when viewed from
       above.
      </documentation>
						</annotation>
					</element>
				</sequence>
			</extension>
		</complexContent>
	</complexType>
	<!-- ====================================================== -->
	<element name="AffinePlacement" type="gml:AffinePlacementType"/>
	<!-- ====================================================== -->
	<complexType name="AffinePlacementType">
		<annotation>
			<documentation> A placement takes a standard geometric
   construction and places it in geographic space. It defines a
   transformation from a constructive parameter space to the 
   co-ordinate space of the co-ordinate reference system being used.  
   Parameter spaces in formulae in this International Standard are 
   given as (u, v) in 2D and(u, v, w) in 3D. Co-ordinate reference 
   systems positions are given in formulae, in this International 
   Standard, by either (x, y) in 2D, or (x, y, z) in 3D.

   Affine placements are defined by linear transformations from 
   parameter space to the target co-ordiante space. 2-dimensional 
   Cartesian parameter space,(u,v) transforms into 3-dimensional co-
   ordinate reference systems,(x,y,z) by using an affine 
   transformation,(u,v)->(x,y,z) which is defined :

	x	ux vx  	x0
			 u	  
	y =	uy vy   + y0
			 v		
	x	uz vz	z0
	
   Then, given this equation, the location element of the 
   AffinePlacement is the direct position (x0, y0, z0), which is the
   target position of the origin in (u, v). The two reference
   directions (ux, uy, uz) and (vx, vy, vz) are the target     
   directions of the unit vectors at the origin in (u, v).
  </documentation>
		</annotation>
		<sequence>
			<element name="location" type="gml:DirectPositionType">
				<annotation>
					<documentation> The “location” property gives 
     the target of the parameter space origin. This is the vector  
    (x0, y0, z0) in the formulae above. 
    </documentation>
				</annotation>
			</element>
			<element name="refDirection" type="gml:VectorType" maxOccurs="unbounded">
				<annotation>
					<documentation> The attribute “refDirection” gives the    
target directions for the co-ordinate basis vectors of the  
parameter space. These are the columns of the matrix in the 
formulae given above. The number of directions given shall be 
inDimension. The dimension of the directions shall be 
outDimension. 
    </documentation>
				</annotation>
			</element>
			<element name="inDimension" type="positiveInteger">
				<annotation>
					<documentation> Dimension of the constructive parameter 
     space.
    </documentation>
				</annotation>
			</element>
			<element name="outDimension" type="positiveInteger">
				<annotation>
					<documentation> Dimension of the co-ordinate space.
    </documentation>
				</annotation>
			</element>
		</sequence>
	</complexType>
	<!-- = global element in "_CurveSegment" substitution group ========================== -->
	<element name="Clothoid" type="gml:ClothoidType" substitutionGroup="gml:_CurveSegment"/>
	<!-- ======================================================================= -->
	<complexType name="ClothoidType">
		<annotation>
			<documentation> A clothoid, or Cornu's spiral, is plane
   curve whose curvature is a fixed function of its length.
   In suitably chosen co-ordinates it is given by Fresnel's
   integrals.

    x(t) = 0-integral-t cos(AT*T/2)dT    
    
    y(t) = 0-integral-t sin(AT*T/2)dT
   
   This geometry is mainly used as a transition curve between
   curves of type straight line to circular arc or circular arc
   to circular arc. With this curve type it is possible to 
   achieve a C2-continous transition between the above mentioned
   curve types. One formula for the Clothoid is A*A = R*t where
   A is constant, R is the varying radius of curvature along the
   the curve and t is the length along and given in the Fresnel 
   integrals.     
  </documentation>
		</annotation>
		<complexContent>
			<extension base="gml:AbstractCurveSegmentType">
				<sequence>
					<element name="refLocation">
						<complexType>
							<sequence>
								<element ref="gml:AffinePlacement">
									<annotation>
										<documentation> The "refLocation" is an affine mapping 
          that places  the curve defined by the Fresnel Integrals  
          into the co-ordinate reference system of this object.
         </documentation>
									</annotation>
								</element>
							</sequence>
						</complexType>
					</element>
					<element name="scaleFactor" type="decimal">
						<annotation>
							<documentation>The element gives the value for the
       constant in the Fresnel's integrals.
      </documentation>
						</annotation>
					</element>
					<element name="startParameter" type="double">
						<annotation>
							<documentation>The startParameter is the arc length
       distance from the inflection point that will be the start
       point for this curve segment. This shall be lower limit
       used in the Fresnel integral and is the value of the
       constructive parameter of this curve segment at its start
       point. The startParameter can either be positive or
       negative. 
       NOTE! If 0.0 (zero), lies between the startParameter and
       the endParameter of the clothoid, then the curve goes
       through the clothoid's inflection point, and the direction
       of its radius of curvature, given by the second
       derivative vector, changes sides with respect to the
       tangent vector. The term length distance for the
      </documentation>
						</annotation>
					</element>
					<element name="endParameter" type="double">
						<annotation>
							<documentation>The endParameter is the arc length
       distance from the inflection point that will be the end
       point for this curve segment. This shall be upper limit
       used in the Fresnel integral and is the value of the
       constructive parameter of this curve segment at its
       start point. The startParameter can either be positive
       or negative.
      </documentation>
						</annotation>
					</element>
				</sequence>