English

An instrument consisting essen­tially of a circle graduated in DEGREES, to which is attached one fixed arm and two arms pivoted at the centre and provided with clamps so that they can be set at any angle to the fixed arm, within the limits of the instrument. It is used for finding a ship's POSITION, when the angles between three fixed and known points are measured. In British terminology, a perspex (or transparent plastic) device used when the MARKS are too close for the use of a STATION POINTER. This instrument has replaced the CUST PROTRACTOR.

In OCEANOGRAPHY and in a morphological sense, a region composed of a group of similar physiographic features whose characteris­tics are markedly in con­trast with surrounding areas (rarely used in marine CARTOGRAPHY).

Instrument used to measure the humidity of the ATMOSPHERE. It comprises two identical THERMO­METERS, the bulb of one of which is dry, while that of the other is wet and covered by a film of pure water or ICE.

The time shift required to align (corre­la­te) a replica of the GPS code generated in the recei­ver with the received GPS code, scaled into distance by the speed of light. This time shift is the diffe­rence between the time of signal reception (measured in the receiver time frame) and the time of emission (measured in the satellite time frame).

An accumulation on the ICE of melt water, mainly due to melting SNOW, but in the more advanced stages also to the melting of ICE. Initial stage con­sists of patches of melted SNOW.

A variation of quantity whose value is normally constant (often zero), the variation being characterized by a rise and a decay. A common example is a very short burst of electromagnetic energy. See WAVE: CONTINUOUS.

The time interval during which the ampli­tude of a pulse is at or greater than a specified value, usually stated in terms of a fraction or per­centage of the maximum value.

System involving the use of prepunched holes in the flat and plate and a set of plastic pins or buttons which are used in registering succeeding flats, positioning the image on the plate, and positioning the plate on the press. See also REGI­STRATION.

A system whose principal feature is that numbers are recorded on cards by means of holes punched in successive columns of a card, the row of the card indicat­ing the digit.

A RADIO STATION which is prepared to provide QTG service, that is to say, to transmit upon request from a ship, a radiosignal, the BEARING of which can be taken by that ship.

A double-reflect­ing instrument for measuring angles. It is similar to a SEXTANT, but has an arc of 90°. Also a surveying or astronomical instrument compo­sed of a graduated arc about 90° in length, equipped with a sighting device.