In surveying, when the Earth's surface is treated as a plane, typically over small areas relative to the Earth's size, the north is assumed to be far enough that all directions toward it can be considered parallel. However, when working over larger areas, directions to the north are aligned along meridians, which converge at the North Pole. This implies that the directions to the north are no longer parallel, and the convergence of the meridians must be accounted for.
In this video lecture, we begin by defining meridian convergence and examining the spherical triangle formed between the north and two selected points. Following this, we discuss the convergence of meridians in relation to planar, spherical, and ellipsoidal datums. We then apply spherical trigonometry to compute corrections due to meridian convergence on a sphere, a principle that can also be extended to the ellipsoid. Finally, we explore the relationship between direct and reverse azimuths on the ellipsoid, illustrated with a numerical example that demonstrates how to calculate the convergence of meridians on an ellipsoidal surface.
Негізгі бет 3-9 Convergence of meridians
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