marmap (version 1.0.10)

get.area: Get projected surface area

Description

Get projected surface area for specific depth layers

Usage

get.area(mat, level.inf, level.sup=0, xlim=NULL, ylim=NULL)

Value

A list of four objects: the projeced surface area in squared kilometers, a matrix with the cells used for calculating the projected surface area, the longitude and latitude of the matrix used for the calculations.

Arguments

mat

bathymetric data matrix of class bathy, imported using read.bathy (no default)

level.inf

lower depth limit for calculation of projected surface area (no default)

level.sup

upper depth limit for calculation of projected surface area (default is zero)

xlim

longitudinal range of the area of interest (default is NULL)

ylim

latitudinal range of the area of interest (default is NULL)

Author

Benoit Simon-Bouhet and Eric Pante

Details

get.area calculates the projected surface area of specific depth layers (e.g. upper bathyal, lower bathyal), the projected plane being the ocean surface. The resolution of get.area depends on the resolution of the input bathymetric data. xlim and ylim can be used to restrict the area of interest. Area calculation is based on areaPolygon of package geosphere (using an average Earth radius of 6,371 km).

See Also

plotArea, plot.bathy, contour, areaPolygon

Examples

## get area for the entire hawaii dataset:
	data(hawaii)
	plot(hawaii, lwd=0.2)
	
	mesopelagic <- get.area(hawaii, level.inf=-1000, level.sup=-200)
	bathyal <- get.area(hawaii, level.inf=-4000, level.sup=-1000)
	abyssal <- get.area(hawaii, level.inf=min(hawaii), level.sup=-4000)
	
	col.meso <- rgb(0.3, 0, 0.7, 0.3) 
	col.bath <- rgb(0.7, 0, 0, 0.3) 
	col.abys <- rgb(0.7, 0.7, 0.3, 0.3) 

	plotArea(mesopelagic, col = col.meso)
	plotArea(bathyal, col = col.bath)
	plotArea(abyssal, col = col.abys)
	
	me <- round(mesopelagic$Square.Km, 0)
	ba <- round(bathyal$Square.Km, 0)
	ab <- round(abyssal$Square.Km, 0)

	legend(x="bottomleft",
		legend=c(paste("mesopelagic:",me,"km2"),
		         paste("bathyal:",ba,"km2"), 
		         paste("abyssal:",ab,"km2")), 
		col="black", pch=21, 
		pt.bg=c(col.meso,col.bath,col.abys))

# Use of xlim and ylim
	data(hawaii)
	plot(hawaii, lwd=0.2)
	
	mesopelagic <- get.area(hawaii, xlim=c(-161.4,-159), ylim=c(21,23),
	                        level.inf=-1000, level.sup=-200)
	bathyal <- get.area(hawaii, xlim=c(-161.4,-159), ylim=c(21,23),
	                        level.inf=-4000, level.sup=-1000)
	abyssal <- get.area(hawaii, xlim=c(-161.4,-159), ylim=c(21,23),
	                        level.inf=min(hawaii), level.sup=-4000)
	
	col.meso <- rgb(0.3, 0, 0.7, 0.3) 
	col.bath <- rgb(0.7, 0, 0, 0.3) 
	col.abys <- rgb(0.7, 0.7, 0.3, 0.3) 
	
	plotArea(mesopelagic, col = col.meso)
	plotArea(bathyal, col = col.bath)
	plotArea(abyssal, col = col.abys)
	
	me <- round(mesopelagic$Square.Km, 0)
	ba <- round(bathyal$Square.Km, 0)
	ab <- round(abyssal$Square.Km, 0)
	
	legend(x="bottomleft",
		legend=c(paste("mesopelagic:",me,"km2"),
		         paste("bathyal:",ba,"km2"), 
		         paste("abyssal:",ab,"km2")), 
		col="black", pch=21, 
		pt.bg=c(col.meso,col.bath,col.abys))