The elevation angle limitations between which usable navigation data may be obtained from a satellite in the doppler mode.
Related Terms 
HARMONIC FUNCTION
Any real function that satisfies a certain equation. In its simplest form, as used in tide and tidal current predictions, it is a quantity that varies as the cosine of an angle that increases uniformly with time

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

GRID RHUMB LINE
A line making the same oblique angle with all grid meridians. Grid parallels and meridians may be considered special cases of the grid rhumb line.

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.

HORIZONTAL DANGER ANGLE
The maximum or minimum angle between two points on a chart, as observed from a vessel, indicating the limit of safe approach to an offlying danger.

BULK MODULUS (OF ELASTICITY)
A ratio of normal stress to a change in volume. A term used in determining the compressibility of a fluid. Data for petroleum products can be found in the International Critical Tables.

GRID NAVIGATION
Navigation by the use of grid directions

HOMING
Navigation toward a point by following a signal from that point. Radiobeacons are commonly used for homing.

PARTICLE EROSION
Occurs when fluidentrained particles moving at high velocity pass through orifices or impinge on metering surfaces or sharp angle turns.

HOUR ANGLE
Angular distance west of a celestial meridian or hour circle; the arc of the celestial equator, or the angle at the celestial pole, between the upper branch of a celestial meridian or hour circle and the hour circl
