English

In ELECTRONIC NAVIGATION, the amount of delay in TIME or PHASE ANGLE introduced by the resi­stivity of the GROUND over which the SIGNAL is pas­sing. In tide terminology, DAILY RETARDATION.

A system of wires, hairs, threa­ds, etched lines, or the like, placed normal to the AXIS of a TELESCOPE at its principal FOCUS, by means of which the TELESCOPE is sighted on a STAR, SIGNAL, or TARGET, or by means of which appropriate readings are made on some SCALE, such as a LEVELLING or STADIA ROD. See also CROSS WIRES, GRATICULE, DIA­PHRAGM. In PHOTOGRAMMETRY, a mark such as a cross or system of lines lying in the image plane of a viewing apparatus and used singly as a refer­ence mark in certain types of monocular instruments or as one of a pair to form a FLOATING MARK as in certain types of STEREOSCOPES.

The ring across which the system of wires, hairs, threads, or the like of a RETICLE are stretched; or the ring which supports the glass DIAPHRAGM when the RETICLE is a system of lines etched on glass.

A LINE OF POSITION which has been moved backward along the COURSE line to correspond with a TIME previous to that at which the line was established. Called a transferred position line in British terminology.

Continuation of RADIANT ENERGY, par­ticularly SOUND by multiple REFLECTION. SOUND scattered towards the source, principally from the ocean surface (surface reverberation) or BOTTOM (bottom reverberation), and from small scattering sources in the medium such as bubbles of air and sus­pended solid matter (volume reverbera­tion).

Facing of stone or other material, either permanent or temporary, placed along the edge of a stream to stabilize the bank and to protect it from the erosive action of the stream.

Motion of a CELESTIAL BODY in its ORBIT; circular motion about an AXIS usually external to the body. The terms revolution and ROTATION are often used interchangeably but, with reference to the motions of a CELESTIAL BODY, revolution refers to the motion in an ORBIT or about an AXIS external to the body, while ROTATION refers to motion about an AXIS within the body. Thus, the EARTH revolves about the SUN annually and rotates about its AXIS daily.

A line on the surface of the EARTH making the same oblique angle with all MERIDIANS; a LOXODROME spiralling toward the POLES in a constant true direc­tion. PARALLELS and MERIDIANS, which also maintain constant true directions, may be considered special cases of the rhumb line. A rhumb line is a straight line on a MERCATOR PROJECTION. Sometimes shortened to rhumb.