Geo-GML
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curve is define as an offset.</documentation>
</annotation>
</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>
</extension>
</complexContent>
</complexType>
<!-- = global element in "_CurveSegment" substitution group = -->
<element name="GeodesicString" type="gml:GeodesicStringType" substitutionGroup="gml:_CurveSegment"/>
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