# TRANSVERSE LONGITUDE

Angular distance between a prime transverse meridian and any given transverse meridian. Also called INVERSE LONGITUDE.

## Related Terms

### MOMENT OF INERTIA

The quantity obtained by multiplying the mass of each small part of a body by the square of its distance from an axis, and adding all the results.

### GREENWICH HOUR ANGLE

Angular distance west of the Greenwich celestial meridian; the arc of the celestial equator, or the angle at the celestial pole, between the upper branch of the Greenwich celestial meridian and the hour circle of a point on the celestial sphere, measured westward from the Greenwich celestial meridian throug

### GREENWICH HOUR ANGLE

Angular distance west of the Greenwich celestial meridian; the arc of the celestial equator, or the angle at the celestial pole, between the upper branch of the Greenwich celestial meridian and the hour circle of a point on the celestial sphere, measured westward from the Greenwich celestial meridian throug

### HALF-POWER POINTS

Power ratios used to define the angular width of a radar beam. One convention defines beam width as the angular width between points at which the field strength is 71 percent of its maximum value. Expressed in terms of power ratio, this convention defines beam width as the angular width between half-power points. A second convention defines beam width as the angular width between points at which the field strength is 50 percent of its maximum value. Expressed in terms of power ratio, the latter convention defines beam width as the angular width between quarter- power points.

### HARPOON LOG

A log which consists of a rotator and distance registering device combined in a single unit, which is towed through the water. The TAFFRAIL LOG is similar except that the registering device is located at the taffrail, with only the rotator in the water.

### GRID MAGNETIC ANGLE

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.

### SHEAR RATE

The difference between the velocities along the parallel faces of a fluid element divided by the distance between the faces.

### GRID NORTH

1. An arbitrary reference direction used with grid navigation. The direction of the 180th geographical meridian from the north pole is used almost universally as grid north. 2. The northerly or zero direction indicated by the grid datum of directional reference.

### HEIGHT OF TIDE

Vertical distance from the chart sounding datum to the water surface at any stage of the tide. It is positive if the water level is higher than the chart sounding datum. The vertical distance from the chart sounding datum to a high water datum is called RISE OF TIDE.

### HOUR CIRCLE

On the celestial sphere, a great circle through the celestial poles. An hour circle through the zenith is called a celestial meridian Also called CIRCLE OF DECLINATION, CIRCLE OF

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