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For a polyline aspect and side are
determined at the segment containing the centroid.
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Node means any node defined for an object.
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For a polygon, end is any single node
on the boundary. Whilst a polygon has a defined start node, its definition is
arbitrary, likely to change with basic manipulation and thus of dubious value.
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An edge match includes the nodes defining that edge.
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The centroid of a region may be outside the region
boundary. (eg. U-shape)
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A point object has all sides and aspects.
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A region object has no sides or aspect definition.
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The end segments of linear objects may be considered
as extending to the limit of data bounds for the purposes of side and aspect.
The actual extent is usually determined by a buffering method.
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Style attributes are only mentioned here because
they can change the apparent (visual) properties of objects. (eg. hide the
boundary of a polygon).
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Object collection properties are a superset of object
properties. eg. A multi-section polyline will contain multiple pairs of ends. A
region is a collection of polygons.
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Principal Axes:
Ixx is the moment of inertia (2nd moment of area) about the x-axis
Iyy is the moment about Y
Ixy is the product of inertia
I1,I2 are principal moments of inertia.
Theta is the angle of the principal axes to the X axis.