Lines of equal variation

Related Terms


Angular difference in direction between grid north and magnetic north. It is measured east or west from grid north. Grid magnetic angle is sometimes called GRID VARIATION or GRIVATION.


A tidal datum midway between mean high water and mean low water. Mean sea level may coincide with half-tide level, but seldom does; the variation is generally about 3 centimeters and rarely exceeds 6 centimeters. Also called MEAN TIDE LEVEL.


An instrument which indicates variation in atmospheric moisture


The amount of variation permitted in the size of a part or other measurable parameter.


1. Unwanted and confusing signals or patterns produced by nearby electrical equipment or machinery, or by atmospheric phenomena. 2. The variation of wave amplitude with distance or time, caused by superposition of two or more waves. Sometimes called WAVE INTERFERENCE.


A chart showing magnetic variation with isogonic lines and the annual rate of change in variation with isoporic lines.


1. An isogram indicating the variation of an element with respect to two variables, one of which is usually the time of year. The other may be time of day, altitude, or some other variable. 2. A line on a map depicting points of constant value of a variable. Examples are contours, isobars, and isogons.


The angular difference between the magnetic meridian and the geographic meridian at a particular location.


Seasonal variation in water level or tidal current speed, more or less periodic due chiefly to meteorological causes


The average period of revolution of the moon from perigee to perigee, a period of 27 days, 13 hours, 18 minutes, and 33.2 seconds in 1900. The secular variation does not exceed a few hundredths of a second per century. anomalistic period. The interval between two successive passes of a satellite through perigee. Also called PERIGEE-TO-PERIGEE PERIOD RADIAL PERIOD. See also ORBITAL PERIOD.

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