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If these lines are a parallel of latitude, as in conical projections, it is called a standard parallel. The central meridian is the meridian to which the globe is rotated before projecting. The central meridian (usually written λ 0) and a parallel of origin (usually written φ 0) are often used to define the origin of the map projection. [22] [23]
A compass needle does not in general point true north. The variation from true north varies with location, and it was suggested that this could provide a basis for determination of longitude. With the exception of magnetic declination, all proved practicable methods. Developments on land and sea, however, were very different.
Definition of the parametric latitude (β) on the ellipsoid. The parametric latitude or reduced latitude, β, is defined by the radius drawn from the centre of the ellipsoid to that point Q on the surrounding sphere (of radius a) which is the projection parallel to the Earth's axis of a point P on the ellipsoid at latitude ϕ.
On a map, the circles of latitude may or may not be parallel, and their spacing may vary, depending on which projection is used to map the surface of the Earth onto a plane. On an equirectangular projection, centered on the equator, the circles of latitude are horizontal, parallel, and equally spaced. On other cylindrical and pseudocylindrical ...
In the United States, the 33rd parallel approximately defines the border between Arkansas and Louisiana. The 33rd parallel north is a circle of latitude that is 33 degrees north of the Earth's equatorial plane. It is approximate at the midpoint between the equator (0 degrees) and the Arctic Circle (66.6 degrees North Latitude.)
The 0° parallel of latitude is designated the Equator, the fundamental plane of all geographic coordinate systems. The Equator divides the globe into Northern and Southern Hemispheres . The longitude λ of a point on Earth's surface is the angle east or west of a reference meridian to another meridian that passes through that point.
The 45th parallel north is often called the halfway point between the equator and the North Pole, but the true halfway point is 16.0 km (9.9 mi) north of it (approximately between 45°08'36" and 45°08'37") because Earth is an oblate spheroid; that is, it bulges at the equator and is flattened at the poles.
The area of low ground itself is the draw, and it is defined by the spurs surrounding it. Draws are similar to valleys on a smaller scale; however, while valleys are by nature parallel to a ridgeline, a draw is perpendicular to the ridge, and rises with the surrounding ground, disappearing up-slope.