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At low frequencies especially, horizontal polarization is avoided. That is because the phase of a horizontally polarized wave is reversed upon reflection by the ground. A distant station in the horizontal direction will receive both the direct and reflected wave, which thus tend to cancel each other. This problem is avoided with vertical ...
D nd (or D nv), [2n,2 +], (2*n) has vertical mirror planes between the horizontal rotation axes, not through them. As a result, the vertical axis is a 2n-fold rotoreflection axis. D nh is the symmetry group for a regular n-sided prism and also for a regular n-sided bipyramid.
The word horizontal is derived from the Latin horizon, which derives from the Greek ὁρῐ́ζων, meaning 'separating' or 'marking a boundary'. [2] The word vertical is derived from the late Latin verticalis, which is from the same root as vertex, meaning 'highest point' or more literally the 'turning point' such as in a whirlpool.
The vertical exaggeration is given by: = where VS is the vertical scale and HS is the horizontal scale, both given as representative fractions.. For example, if 1 centimetre (0.39 in) vertically represents 200 metres (660 ft) and 1 centimetre (0.39 in) horizontally represents 4,000 metres (13,000 ft), the vertical exaggeration, 20×, is given by:
The definitions and results in this section are taken from the 1913 text Plane and Solid Geometry by George A. Wentworth and David Eugene Smith (Wentworth & Smith 1913).. A cylindrical surface is a surface consisting of all the points on all the lines which are parallel to a given line and which pass through a fixed plane curve in a plane not parallel to the given line.
When dealing with toric lenses, the axis defines the orientation of the steepest and flattest curvatures relative to horizontal and vertical. The "3 o'clock" position is defined as zero, and the 90th meridian is a vertical line. A horizontal line passes through both zero and the 180th meridians. By convention, a horizontal axis is recorded as 180.
The prism paralleloscope entered service with the British Army in the late 1950s. It was permanently fitted in a fibre-glass case with a lid. This case was mounted on two short metal vertical poles so that it was about 2 ft (0.6 m) above the ground, these vertical poles were held together by two horizontal rods slightly shorter than the paralleloscope case.
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