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perpendicular bisector

The perpendicular bisector of a line segment AB is the straight line perpendicular to AB through the midpoint of AB.

Maritime Boundaries

Maritime Boundaries   Reference library

The Oxford Encyclopedia of Maritime History

Reference type:
Subject Reference
Current Version:
2007
Subject:
History, Military History
Length:
3,256 words

...circumstance that has been taken into account is the general direction of the relevant coasts. This basically entails simplifying the coastal configuration by constructing one or more straight lines along these coasts and then drawing a perpendicular—if there is a single line representing all relevant coasts—or a bisector of the angle if there are two intersecting lines representing the general directions of the relevant coasts. The exclusive economic zone and the continental shelf overlap spatially within two hundred nautical miles. Both zones include the...

Nautical Astronomy and Celestial Navigation

Nautical Astronomy and Celestial Navigation   Reference library

The Oxford Encyclopedia of Maritime History

Reference type:
Subject Reference
Current Version:
2007
Subject:
History, Military History
Length:
12,412 words
Illustration(s):
6

...Wherever the observer stands, the ground is a plane perpendicular to the observer’s body, a plane that extends outward infinitely. The “poles” of the observer are the zenith, the point on the celestial sphere directly overhead, and the nadir, the point directly below the observer, also in a line perpendicular to the horizon plane. A celestial sphere may feature a number of vertical circles. The great circle intersecting the poles and passing through the observer’s zenith is the principal vertical. Perpendicular to the principal vertical, and passing through east...

Navigational Instruments

Navigational Instruments   Reference library

The Oxford Encyclopedia of Maritime History

Reference type:
Subject Reference
Current Version:
2007
Subject:
History, Military History
Length:
30,532 words
Illustration(s):
5

...Through a complex procedure of bisections and the use of a “scale of equal parts” he was able to lay out angles of 60°, 90°, 75°, and 85°20'. The 85°20' point was the critical step, and it had to be carefully confirmed. Once this point was established it could be bisected into the 1,024 remaining points, dividing the arc into five-minute graduations. An additional series of bisections completed the fifty-six remaining graduations between 85°20' and 90°—a test of skill which very few makers could complete successfully. The Board of Longitude gave Bird an award...

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