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Railway Direction
Railroad directions are used to describe train directions on rail systems. The terms used may be derived from such sources as compass directions, altitude directions, or other directions. However, the railroad directions frequently vary from the actual directions, so that, for example, a "northbound" train may really be headed west over some segments of its trip, or a train going "down" may actually be increasing its elevation. Railroad directions are often specific to system, country, or region. Radial directions Many rail systems use the concept of a center (usually a major city) to define rail directions. Up and down In British practice, railway directions are usually described as "up" and "down", with "up" being towards a major location. This convention is applied not only to the trains and the tracks, but also to items of lineside equipment and to areas near a track. Since British trains run on the left, the "up" side of a line is usually on the left when proceeding in the "u ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Centre (geometry)
In geometry, a centre (or center; ) of an object is a point in some sense in the middle of the object. According to the specific definition of center taken into consideration, an object might have no center. If geometry is regarded as the study of isometry groups, then a center is a fixed point of all the isometries that move the object onto itself. Circles, spheres, and segments The center of a circle is the point equidistant from the points on the edge. Similarly the center of a sphere is the point equidistant from the points on the surface, and the center of a line segment is the midpoint of the two ends. Symmetric objects For objects with several symmetries, the center of symmetry is the point left unchanged by the symmetric actions. So the center of a square, rectangle, rhombus or parallelogram is where the diagonals intersect, this is (among other properties) the fixed point of rotational symmetries. Similarly the center of an ellipse or a hyperbola is where the axes i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
