Name

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LAND_MASK

Purpose

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This function creates and returns a global gridded land mask of
the desired resolution.

Category

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Geographical

Calling Sequence

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Result = LAND_MASK( )

Keyword Parameters

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AFRICA: If set the function returns a mask of the African
landmass only. Note this may not properly isolate
Africa from Eurasia at some resolutions.
ANTARCTICA: If set the function returns a mask of the Antarctic
landmass only.
AUSTRALIA: If set the function returns a mask of the Australian
landmass only.
EURASIA: If set the function returns a mask of the Eurasian
landmass only. Note this may not properly isolate
Eurasia from Africa at some resolutions.
LATITUDE: Returns a vector of the latitude coordinates of the
grid points.
LIMIT: The coordinates of the corner points of the grid, of
type floating point. This vector is of the form
[ westernmost longitude, southernmost latitude,
easternmost longitude, northernmost latitude].
The default is [ -180, -90, 180, 90 ].
LONGITUDE: Returns a vector of the longitude coordinates of
the grid points.
NAMERICA: If set the function returns a mask of the North
American landmass only.
RESOLUTION: The scalar resolution of the uniform grid in degrees.
If a 2-element vector it defines the resolution for
[ longitude, latitude ]. The default is 1x1 degree.
SAMERICA: If set the function returns a mask of the South
American landmass only.
SEED: The [lon,lat] coordinates of a single desired landmass.
The function returns a mask of all contiguous land
surrounding this point.
WALL: A 4-element vector (or 4xN-element array) of coordinates
of wall(s) to separate landmasses when using SEED (e.g.
to separate South America from North America). The
coordinates are of the form [ lon1, lat1, lon2, lat2 ].

Outputs

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Result: A longitude x latitude land mask grid. Points
corresponding to land are denoted by "1", "0"
otherwise.
LATITUDE, LONGITUDE

Uses

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dimension.pro
sign.pro

Procedure

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This function plots a global map in a virtual window and
determines which points are coloured as land. If SEED is set,
it uses an algorithm expanding from the SEED point to determine
contiguous points.

Example

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Return a 1x1-degree global land grid.
Result = land_mask( )

Modification History

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  Written by: Daithi A. Stone (stoned@atm.ox.ac.uk), 2000-07-25.
Modified: DAS, 2000-08-22 (killed grid size bug).
Modified: DAS, 2000-08-29 (improved continent definitions;
killed WALL bug).
Modified: DAS, 2004-03-10 (altered to work with TrueColor).
Modified: DAS, 2006-07-25 (modified documentation; fixed bug
where end LATITUDE values are on top of poles;
removed use of constants.pro)