marmap (version 1.0.10)

get.box: Get bathymetric information of a belt transect

Description

get.box gets depth information of a belt transect of width width around a transect defined by two points on a bathymetric map.

Usage

get.box(bathy,x1,x2,y1,y2,width,locator=FALSE,ratio=FALSE, ...)

Value

A matrix containing depth values for the belt transect. rownames indicate the kilometric distance from the start of the transect and colnames indicate the distance form the central transect in degrees. If ratio=TRUE, a list of two elements: depth, a matrix containing depth values for the belt transect similar to the description above and ratios a vector of length two specifying the ratio between (i) the width and length of the belt transect and (ii) the depth range and the length of the belt transect. These ratios can be used by the function wireframe to produce realistic 3D bathymetric plots of the selected belt transect.

Arguments

bathy

Bathymetric data matrix of class bathy.

x1

Numeric. Start longitude of the transect. Requested when locator=FALSE.

x2

Numeric. Stop longitude of the transect. Requested when locator=FALSE.

y1

Numeric. Start latitude of the transect. Requested when locator=FALSE.

y2

Numeric. Stop latitude of the transect. Requested when locator=FALSE.

width

Numeric. Width of the belt transect in degrees.

locator

Logical. Whether to choose transect bounds interactively with a map or not. When FALSE (default), a bathymetric map (plot.bathy(bathy,image=TRUE)) is automatically plotted and the position of the belt transect is added.

ratio

Logical. Should aspect ratio for the wireframe plotting function (package lattice) be computed (default is FALSE).

...

Other arguments to be passed to locator and lines to specify the characteristics of the points and lines to draw on the bathymetric map for both the transect and the bounding box of belt transect.

Author

Benoit Simon-Bouhet and Eric Pante

Details

get.box allows the user to get depth data for a rectangle area of the map around an approximate linear transect (belt transect). Both the position and size of the belt transect are user defined. The position of the transect can be specified either by inputing start and stop coordinates, or by clicking on a map created with plot.bathy. In its interactive mode, this function uses the locator function (graphics package) to retrieve and plot the coordinates of the selected transect. The argument width allows the user to specify the width of the belt transect in degrees.

See Also

plot.bathy, get.transect, get.depth

Examples

# load and plot bathymetry
	data(hawaii)
	plot(hawaii,im=TRUE)

# get the depth matrix for a belt transect
	depth <- get.box(hawaii,x1=-157,y1=20,x2=-155.5,y2=21,width=0.5,col=2)
	
# plotting a 3D bathymetric map of the belt transect
	require(lattice)
	wireframe(depth,shade=TRUE)
	
# get the depth matrix for a belt transect with realistic aspect ratios
	depth <- get.box(hawaii,x1=-157,y1=20,x2=-155.5,y2=21,width=0.5,col=2,ratio=TRUE)

# plotting a 3D bathymetric map of the belt transect with realistic aspect ratios
	require(lattice)
	wireframe(depth[[1]],shade=TRUE,aspect=depth[[2]])