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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.

Thiessen polygon

Thiessen polygon   Quick reference

A Dictionary of Geography (5 ed.)

Reference type:
Subject Reference
Current Version:

...polygon A subdivision of a drainage basin, containing a rain gauge. Polygons are constructed by first siting the rain gauges, plotting them on a base map, and connecting the sites by straight lines. The lines are bisected with perpendiculars, which meet to form the polygons. The areas of the polygons are calculated and expressed as fractions of the total area. Each fraction is multiplied by the precipitation recorded by its rain gauge. The sum of these calculations represents total precipitation over the catchment area. For an account, see Yoo et al....

folds and folding

folds and folding   Reference library

The Oxford Companion to the Earth

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Subject Reference
Current Version:
Science and technology, Earth Sciences and Geography
2,109 words

...The axial surface is an imaginary surface that connects the hinge zones of the various folded layers and commonly bisects the angle between adjacent fold limbs. The shape of a fold is a function of the thickness of a layer with respect to a referent; for example a thickness measured at right angles to the surface of a layer (Fig. 3) or the thickness of the axial surface. If the thickness of a particular layer is constant normal (perpendicular) to the layer, the shape of the fold is parallel . If the thickness is constant parallel to the axial surface, the...