Outdoor Glossary: G

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(1) Steel wire-mesh basket to hold stones or crushed rock to protect a bank or bottom from erosion. (2) (SMP) Structures composed of masses of rocks, rubble or masonry held tightly together usually by wire mesh so as to form blocks or walls. Sometimes used on heavy erosion areas to retard wave action or as a foundation for breakwaters or jetties.

See tide gauge.

A wind between a strong breeze and a storm. A continuous wind blowing in degrees of moderate, fresh, strong, or whole gale and varying in velocity from 28 to 30 nautical miles per hour.

The space on a boat that would be referred to as the kitchen

gallinaceous birds
synonymous with upland game birds.

A whirlpool in the Strait of Messina; at one time called Charybdis.

game animal
any wild animal that can be legally hunted or trapped.

game species
Any species of wildlife or fish that is harvested according to prescribed limits and seasons.

A special rig used for bottom fishing that utilizes multiple hooks in return giving the angler the ability to catch more than one fish at a time

The area between the point and the shank of a hook

Base of the bill where the mandibles join. Synonym(s): commissure, rictus.

Primitive ray-finned freshwater fishes of North and Central America and Cuba. Characterized by elongated jaws and heavy ganoid scales.

gas purged pressure gauge
A type of analog tide gauge in which gas, usually nitrogen, is emitted from a submerged tube at a constant rate. Fluctuations in hydrostatic pressure due to changes in tidal height modify the emission rate for recording. Same as bubbler tide gauge.

A device for measuring the water level relative to a datum.

Any tools used to catch fish, such as hook and line, trawls, gill nets, traps, spears, etc

gear ratio
In reference to the amount of times that the spool of a reel rotates while the handle is rotated once.

generating area
In wave forecasting, a continuous area of the water surface over which the wind blows in essentially the same direction. Sometimes used synonymously with fetch length.

generating force mechanism
Causing waves formation such as gravitational attraction.

generation of waves
(1) The creation of waves by natural or mechanical means. (2) The creation of and growth of waves by a wind blowing over a water surface for a certain length of time. The area involved is called the generating area or fetch.

geodesy (or geodetics)
The science of dealing with the investigation of scientific questions connected with the shape and dimensions of the Earth.

geodetic datum
See National Geodetic Vertical Datum of 1929.

Geographic Information System (GIS)
A system of spatially referenced information, including computer programs that acquire, store, manipulate, analyze, and display spatial data.

The equipotential surface of the Earths gravity field which best fits, in the least squares sense, mean sea level.

The science which treats of the origin, history and structure of the Earth, as recorded in rocks; together with the forces and processes now operating to modify rocks.

geomorphic processes
Processes that change the form of the earth, such as volcanic activity, running water, and glacial action.

(1) That branch of physical geography which deals with the form of the Earth, the general configuration of its surface, the distribution of the land, water, etc. (2) The investigation of the history of geologic changes through the interpretation of topographic forms.

The study of the physical characteristics and properties of the Earth.

The unit of geopotential difference, equal to the gravity potential of 1 meter squared per second squared, m / s, or 1 joule per kilogram, J / kg.

geopotential (equipotential) surface
A surface that is everywhere normal to the acceleration of gravity.

geopotential anomaly (delta D)
The excess in geopotential difference over the standard geopotential difference [at a standard specific volume at 35 parts per thousand (/..) and 0 degrees C] between isobaric surfaces. See geopotential and geopotential topography.

geopotential difference
The work per unit mass gained or required in moving a unit mass vertically from one geopotential surface to another. See geopotential, geopotential anomaly, and geopotential topography.

geopotential topography
The topography of an equiscalar (usually isobaric) surface in terms of geopotential difference. As depicted on maps, isopleths are formed by the intersection of the isobaric surface with a series of geopotential surfaces. Thus, the field of isopleths represents variations in the geopotential anomaly of the isobaric surface above a chosen reference isobaric surface (such as a level of no motion).

geostrophic flow
A solution of the relative hydrodynamic equations of motion in which it is assumed that the horizontal component of the Coriolis force is balanced by the horizontal component of the pressure gradient force.

gestation period
the period of time during which young develop inside the mother's body prior to birth. The gestation period for a human is 9 months, while the gestation period for a red fox is 7-1/2 weeks.

Respiratory organ of many aquatic animals; a filamentous outgrowth well supplied with blood vessels at which gas exchange between water and blood occurs.

gill membranes
Membranes along the ventral and posterior margin of the operculum (gill cover) which function in respiration; they are supported by the branchiostegal rays

gill nets
A flat net suspended vertically in the water with meshes that allow the head of a fish to pass but entangle it at withdrawal; invented circa 800 A.D. and used extensively by Native American fishers in the Great Lakes region.

gill rakers
Bony, finger-like projection of the gill arch on the opposite side from the red gill filaments which function in retaining food organisms; they vary greatly in number and length and are important in the classifications and identification of fishes

A pair of rings and axles that will keep an object along a level plane regardless of the pitch and movement of the object to which the gimbals are anchored

GIS (geographic information systems)
GIS is both a database designed to handle geographic data as well as a set of computer operations that can be used to analyze the data. In a sense, GIS can be thought of as a higher order map.

Global Positioning System (GPS)
A navigational and positioning system developed by the U.S. Department of Defense, by which the location of a position on or above the Earth can be determined by a special receiver at that point interpreting signals received simultaneously from several of a constellation of special satellites.

Lowermost ridge on lower mandible.

graded bedding
An arrangement of particle sizes within a single bed, with coarse grains at the bottom of the bed and progressively finer grains toward the top of the bed.

(1) A measure of slope (soil- or water-surface) in meters of rise or fall per meter of horizontal distance. (2) More general, a change of a value per unit of distance, e.g. the gradient in longshore transport causes erosion or accretion. (3) With reference to winds or currents, the rate of increase or decrease in speed, usually in the vertical; or the curve that represents this rate.

gradient flow
A solution of the relative hydrodynamic equations of motion in which only the horizontal Coriolis, pressure gradient, and centrifugal forces are considered.

An extremely light and flexible material used to make rod blanks and rod components

grass carp
rather slim body. Dark green to brownish above; yellowish below. Frontal mouth with no barbels. Large scales. Size: Most are 5-15 pounds; potential much larger. World record 65 pounds, 14 ounces

(1) Loose, rounded fragments of rock, larger than sand, but smaller than cobbles. (2) Small stones and pebbles, or a mixture of these with sand.

gravitational tide
Same as equilibrium tide.

gravity wave
A wave whose velocity of propagation is controlled primarily by gravity. Water waves more than 5 cm long are considered gravity waves. Waves longer than 2.5 cm and shorter than 5 cm are in an indeterminate zone between capillary and gravity waves. See ripple.

great diurnal range (Gt)
The difference in height between mean higher high water and mean lower low water. The expression may also be used in its contracted form, diurnal range.

great tropic range (Gc)
The difference in height between tropic higher high water and tropic lower low water. The expression may also be used in its contracted form, tropic range.

greater secondary coverts
Feathers overlying bases of secondaries.

Greenwich argument
Equilibrium argument computed for the meridian of Greenwich.

Greenwich interval
An interval referred to the transit of the Moon over the meridian of Greenwich as distinguish from the local interval which is referred to the Moon's transit over the local meridian. The relation in hours between Greenwich and local intervals may be expressed by the formula: Greenwich interval = local interval + 0.069 L where L is the west longitude of the local meridian in degrees. For east longitude, L is to be considered negative.

Gregorian calendar
The modern calendar in which every year divisible by 4 (excepting century years) and every century year divisible by 400 are bissextile (or leap) years with 366 days. All other years are common years with 365 days. The average length of this year is, therefore, 365.242,5 days which aggrees very closely with the length of the tropical year (the period of changes in the seasons). The Gregorian calendar was introduced by Pope Gregory in 1582, and immediately adopted by the Catholic countries in place of the Julian calendar previously in use. In making the change it was ordered that the day following October 4, 1582, of the Julian calendar be designated October 15, 1582, of the Gregorian calendar; the 10 days being dropped in order that the vernal equinox would fall on March 21. The Gregorian calendar was not adopted by England until 1752, but is now in general use throughout the world.

(1) A shore-protection structure (built usually to trap littoral drift or retard erosion of the shore). It is narrow in width (measured parallel to the shore) and its length may vary from tens to hundreds of meters (extending from a point landward of the shoreline out into the water). groins may be classified as permeable (with openings through them) or impermeable (a solid or nearly solid structure). (2) (SMP) A barrier-type structure extending from the backshore or stream bank into a water body for the purpose of the protection of a shoreline and adjacent upland by influencing the movement of water and/or deposition of materials.

groin bay
The beach compartment between two groins.

groin system
A series of groins acting together to protect a section of beach. Commonly called a groin field.

ground fire
A fire that burns along the forest floor and does nor affect trees with thick bark or high crowns.

ground Penetrating Radar (GPR)
A geophysical technology that uses radio waves to detect buried objects and the internal structure of landforms. Ground swell: (1) Long high swell in deep water. (2) Also, this swell as if rises to prominent height in shoal water.

ground water
Subsurface water occupying the zone of saturation. In a strict sense the term applied only to water below the water table.

Fishes that primarily inhabit the benthic environment, such as flatfish

group selection
A method of tree harvest in which trees are removed periodically in small groups. This

group velocity
The velocity at which a wave group travels. In deep water, it is equal to one-half the individual wave velocity.

Guiana Current
An Atlantic Ocean current setting northwestward along the north-east coast of South America.

The loops on a rod through which the line runs

Guinea Current
An Atlantic Ocean current setting eastward along the west central coast of Africa. A continuation of the Equatorial Counter Current of the Atlantic Ocean.

Behind the chin and between the sides of the lower jaw

gular region
Between the chin and the foreneck.

Local name given to the double low water occurring on the south coast of England. See double tide.

A relatively large portion of sea, partly enclosed by land.

Gulf Coast Low Water Datum (GCLWD)
A tidal datum. Used as chart datum from November 14, 1977, to November 27, 1980, for the coastal waters of the Gulf coast of the United States. GCLWD is defined as mean lower low water when the type of tide is mixed and mean low water (now mean lower low water) when the type of tide is diurnal. See National Tidal Datum Convention of 1980.

Gulf Coast Low Water Datum line
The line on a chart or map which represents the intersection of the land with the water surface at the elevation of Gulf Coast Low Water Datum.

Gulf Stream
A North Atlantic Ocean current setting northeastward off the east coast of the United States. A segment of the Gulf Stream System, the Gulf Stream extends from the region off Cape Hatteras to an area southeast of the Grand Banks at about latitude 40 north, longitude 50 west. It continues the flow of the Florida Current to the North Atlantic Current.

Gulf Stream System
The continuous current system composed of the Florida Current, Gulf Stream, and North Atlantic Current.

refers to all Larus and Rissa (Family Laridae). True gulls and kittiwakes.

The alimentary canal. A term used when describing fish larvae

(1) A narrow passage such as a strait or inlet. (2) A channel in otherwise shallow water, generally formed by water in motion.

Flat-topped seamount.


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