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The thalweg of a river. In geography, hydrography, and fluvial geomorphology, a thalweg or talweg (/ ˈ t ɑː l v ɛ ɡ /) is the line or curve of lowest elevation within a valley or watercourse. [1] Its vertical position in maps is the nadir (greatest depth, sounding) in the stream profile.
On a Mercator projection map, any rhumb line is a straight line; a rhumb line can be drawn on such a map between any two points on Earth without going off the edge of the map. But theoretically a loxodrome can extend beyond the right edge of the map, where it then continues at the left edge with the same slope (assuming that the map covers ...
More generally, when both of the segment's end points are vertices of a polygon or polyhedron, the line segment is either an edge (of that polygon or polyhedron) if they are adjacent vertices, or a diagonal. When the end points both lie on a curve (such as a circle), a line segment is called a chord (of that curve).
Thus, we would say that two different points, A and B, define a line and a decomposition of this line into the disjoint union of an open segment (A, B) and two rays, BC and AD (the point D is not drawn in the diagram, but is to the left of A on the line AB). These are not opposite rays since they have different initial points.
The vertices of the arrangement are isolated points belonging to two or more lines, where those lines cross each other. [1] The boundary of a cell is the system of edges that touch it, and the boundary of an edge is the set of vertices that touch it (one vertex for a ray and two for a line segment).
Position resection and intersection are methods for determining an unknown geographic position (position finding) by measuring angles with respect to known positions.In resection, the one point with unknown coordinates is occupied and sightings are taken to the known points; in intersection, the two points with known coordinates are occupied and sightings are taken to the unknown point.
The Horseshoe Falls, one of the three Niagara Falls.The falls are a knickpoint, formed by slower erosion above the falls than below. In geomorphology, a knickpoint or nickpoint is part of a river or channel where there is a sharp change in channel bed slope, such as a waterfall or lake.
In differential geometry, conjugate points or focal points [1] [2] are, roughly, points that can almost be joined by a 1-parameter family of geodesics. For example, on a sphere, the north-pole and south-pole are connected by any meridian. Another viewpoint is that conjugate points tell when the geodesics fail to be length-minimizing.