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A prime meridian is an arbitrarily chosen meridian (a line of longitude) in a geographic coordinate system at which longitude is defined to be 0°. On a spheroid, a prime meridian and its anti-meridian (the 180th meridian in a 360°-system) form a great ellipse.
From 1884 to 1974, the Greenwich meridian was the international standard prime meridian, used worldwide for timekeeping and navigation. The modern standard, the IERS Reference Meridian, is based on the Greenwich meridian, but differs slightly from it. [1] This prime meridian (at the time, one of many) was first established by Sir George Airy ...
In the following series is the difference of the longitude of an arbitrary point and the longitude of the chosen central meridian: is in radians and is positive east of the central meridian. The W coefficients are functions of ϕ {\displaystyle \phi } listed below .
The figure on the left shows how a transverse cylinder is related to the conventional graticule on the sphere. It is tangential to some arbitrarily chosen meridian and its axis is perpendicular to that of the sphere. The x- and y-axes defined on the figure are related to the equator and central meridian exactly as they are for the normal ...
Figure 1. This BLM map depicts the principal meridians and baselines used for surveying states (colored) in the PLSS.. The following are the principal and guide meridians and base lines of the United States, with the year established and a brief summary of what areas' land surveys are based on each.
Meridian arc, the distance between two points with the same longitude; Prime meridian, origin of longitudes; Principal meridian, arbitrary meridians used as references in land surveying; Meridian line, used with a gnomon to measure solar elevation and time of year; Autonomous sensory meridian response, a static-like or tingling sensation on the ...
Eratosthenes in the 3rd century BC first proposed a system of latitude and longitude for a map of the world. His prime meridian (line of longitude) passed through Alexandria and Rhodes, while his parallels (lines of latitude) were not regularly spaced, but passed through known locations, often at the expense of being straight lines. [1]
The most important reason for the 5.3 seconds of longitude offset between the IERS Reference Meridian and the Airy transit circle is that the observations with the transit circle were based on the astronomical longitude, while the IERS Reference is a geodetic-based longitude, that is, the plane of the meridian contains the center of figure of the Earth. [1]