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Eng ID Term Definition
5201
sunset
The crossing of the APPARENT HORIZON by the upper LIMB of the descending SUN.
5202
sunshine recorder
See HELIOGRAPH.
5203
sunspot
Any of the dark spots sometimes seen at the surface of the SUN; they are believed to have some connection with magnetic disturban­ces on EAR... more
Any of the dark spots sometimes seen at the surface of the SUN; they are believed to have some connection with magnetic disturban­ces on EARTH.
5204
sunspot cycle
The time interval (11.2 YEARS) during which the number of SUNSPOTS progresses from a minimum to a maximum and decreases again to a minimum.
5205
super high frequency (SHF)
See FREQUENCY: RADIO.
5206
superior conjunction
See CONJUNCTION.
5207
superior mirage
See MIRAGE.
5208
superior planet(s)
See PLANET(S): SUPERIOR.
5209
superior transit
See MERIDIAN TRANSIT.
5210
superjacent waters
The waters lying immediately above the sea-bed or deep ocean floor up to the surface.
5211
super-short baseline acoustic system
A variation of the short baseline system with three sensors incorpo­rated in a single transducer.
5212
supersonic
(adj.). Designating or of a SPEED greater than the SPEED of SOUND.
5213
supplemental control
See CONTROL.
5214
supplemental control point
A photoimage point for which an ELEVATION or a horizontal POSITION, or both, is to be, or has been determined. See also CONTROL POINT.
5215
supplementary station
See STATION.
5216
surf
Collective term for BREAKERS. The wave activity in the area between the SHORELINE and the outermost limit of BREAKERS.
5217
surface boundary layer
See GROUND LAYER.
5218
surface current
See CURRENT.
5219
surface duct
A zone immediately below the sea surface where SOUND RAYS are refracted toward the surface and then reflected. They are refracted because th... more
A zone immediately below the sea surface where SOUND RAYS are refracted toward the surface and then reflected. They are refracted because the SOUND VELOCITY at some DEPTH near the surface is greater than at the surface. The RAYS alternately are refrac­ted and reflected along the duct to considerable distances from the sound source.
5220
surface mark
A STATION MARK used in addition to the UNDERGROUND MARK, over which it is plumbed.