Glossary

Popular terms used throughout this website

 


MARSH, COASTAL

Area of salt-tolerant vegetation in brackish and (or) saline-water habitants subject to tidal inundation.

MARSH, FRESHWATER

Tract of low wet ground, usually miry and covered with rank vegetation.

MEAN HIGH WATER

Tidal datum that is the arithmetic mean of the high water heights observed over a specific 19-year Metonic cycle (National Tidal Datum Epoch). For stations with shorter series, simultaneous observations are made with a primary control tide station to derive the equivalent of a 19-year value. Use of "mean high tide" is discouraged.

Mean High Water Line: Intersection of the land with the water surface at the elevation of high water.

MEAN LOW WATER

Tidal datum that is the arithmetic mean of the low water heights observed over a specific 19-year Metonic cycle (National Tidal Datum Epoch). For stations with shorter series, simultaneous observations are made with a primary control tide station to derive the equivalent of a 19-year value. Use of "mean low tide" is discouraged.

Mean Low Water Line: Intersection of the land with the water surface at the elevation of low water. 

MEAN SEA LEVEL

Tidal datum that is the arithmetic mean of the hourly water elevations observed over a specific 19-year Metonic cycle (National Tidal Datum Epoch). Shorter series are specified in the name; that is, monthly mean sea level and yearly mean sea level.

MEANDER LINE

Metes-and-bounds traverse approximately along the mean high water line of a permanent body of water. By following the sinuosities of the bank or shoreline, the meander line provides data for computing the area of land remaining after the water area has been segregated. A meander line differs from other metes and bounds surveys in that it does not ordinarily determine or fix boundaries.

MERIDIAN

Great circle on the surface of the Earth passing through the geographical poles and any given point on the Earth's surface. All points on a given meridian have the same longitude.

METADATA

For formats other than NITF, the metadata is supplied as separate files on the delivered media. The metadata contains the information needed to ingest the image/data into a GIS software. If there are problems reading the imagery, the solution may lie in the metadata.

METES AND BOUNDS

Method of describing land by measure of length (metes) of the boundary lines (bounds).

METONIC CYCLE

Period of 235 lunations or about 19 years. devised by Meton, an Athenian astronomer (5th century B.C.) for the purpose of obtaining a period at the end of which the phases of the moon recur in the same order and on the same days as in the preceding cycle.

METRIC SYSTEM

Decimal system of weights and measures based on the meter as a unit length and the kilogram as a unit mass. 

MONOSCOPIC

Pertaining to the observation of a single photograph or other view.

MONUMENT (SURVEYING)

Permanent physical structure marking the location of a survey point. Common types of monuments are inscribed metal tablets set in concrete posts; and metal rods driven in the ground.

MOSAIC, AERIAL

Assembly of aerial photographs whose edges usually have been torn or cut selectively and matched to the imagery on adjoining photographs to form a continuous representation of a portion of the Earth's surface.

MULTIPLEX

Stereoplotter of the double-projection type characterized by its use of reduced- scale diapositives and stationary lamphouses with condensing lenses.