English

Used in Mercator projection charts to indicate the parallel at which the noted scale of the chart is exact. The scale parallel itself need not necessarily be depicted within the chart.

The relation between an in­finitesi­mal linear distance in any direction at any point on a map PROJECTION and the corresponding linear distance on a GLOBE.

A SCALE involving a relatively large reduction in size. A small scale chart is one covering a large area. The opposite is LARGE SCALE. See SCALE: NATURAL.

A graphic SCALE by means of which the rate of SPEED of a SURVEY SHIP, or the distance tra­velled in a given time can be determined quickly and accura­tely.

A multiplier for reducing a distance obtained from a MAP by computation or scaling to the actual distance on the DATUM of the MAP. A conventional modification which may be applied to the majority of map PROJECTIONS. This is the multipli­cation of the PRINCIPAL SCALE by some numerical con­stant which is slightly less than unity. This has the effect of changing all PARTICULAR SCALES by a corre­sponding amount and, since both maximum and minimum PAR­TICULAR SCALES are similarly modified, the special properties of the PROJECTION are unaffected. The effect is to produce a better balance of positive and negative SCALE ERRORS over the mapped area.

That SCALE at which the POSITIONS of the SOUNDINGS in the area are plotted on the HYDROGRAPHIC SURVEY SHEET. Suitable survey scales are selected in each case in accordance with the nature of the SURVEY and the average DEPTHS prevailing in the area.

A device for directing a BEAM of RADIANT ENERGY successively over all points of a given region. In data processing a photo-electronic device for digital reproduction of pictures. The picture is scan­ned linewise and decomposed into a matrix-like raster of individual pixels. In contrast to vectorial DIGITI­ZERS, the information to coherent elements of the picture (lines, symbols) is lost by this rasteriza­tion process. To retrieve these elements the rasterized picture has to be vectorized by pattern recognition methods and manual post-processing.

In physics, the change in direction of a particle or WAVE, because of a collision with another particle or system. In electromagnetism, diffusion of ELECTROMAGNETIC WAVES in a random manner by air masses in the upper ATMOSPHERE. See also: TROPOSPHERIC SCATTERING.

Upward motion of a vessel, either upward motion of the bow and stern associated with pitching, or lifting of the entire vessel by WAVES or SWELL, when it may be called send.

A foliated metamor­phic ROCK which can be split into thin flakes or flat lenticles. Schists are usual­ly named from the dominant mineral, e.g. mica schist.

The face of a CATHODE-RAY TUBE of electronic equipment. The various methods of presenting the information on a radar scope are usually designated by letter, as A-scope, B-scope, etc. Also called INDICA­TOR,scan, SCREEN, although the alphabetical designa­tions are not generally used with SCREEN.