marmap (version 1.0.10)

get.transect: Compute approximate cross section along a depth transect

Description

Compute the depth along a linear transect which bounds are specified by the user.

Usage

get.transect(mat, x1, y1, x2, y2, locator=FALSE, distance=FALSE, ...)

Value

A table with, at least, longitude, latitude and depth along the transect, and if specified (distance=TRUE), the distance in kilometers from the start of the transect. The number of elements in the resulting table depends on the resolution of the bathy object.

Arguments

mat

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

x1

start longitude of the transect (no default)

x2

stop longitude of the transect (no default)

y1

start latitude of the transect (no default)

y2

stop latitude of the transect (no default)

locator

whether to use locator to choose transect bounds interactively with a map (default is FALSE)

distance

whether to compute the haversine distance (in km) from the start of the transect, along the transect (default is FALSE)

...

other arguments to be passed to locator() to specify the characteristics of the points and lines to draw on the bathymetric map when locator=TRUE.

Author

Eric Pante and Benoit Simon-Bouhet

Warning

Clicking once or more than twice on the map will return a warning message: "Please choose only two points from the map". Manually entering coordinates that are outside the geographical range of the input bathy matrix will return a warning message.

Details

get.transect allows the user to compute an approximate linear depth cross section 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); after creating a map with plot.bathy, the user can click twice to delimit the bound of the transect of interest (for example, lower left and upper right corners of a rectangular area of interest), press Escape, and get a table with the transect information.

See Also

read.bathy, nw.atlantic, nw.atlantic.coast, get.depth, get.sample

Examples

	
# load datasets
	data(nw.atlantic); as.bathy(nw.atlantic) -> atl
	data(nw.atlantic.coast)

# Example 1. get.transect(), without use of locator()
	get.transect(atl, -65, 43,-59,40) -> test ; plot(test[,3]~test[,2],type="l")
	get.transect(atl, -65, 43,-59,40, distance=TRUE) -> test ; plot(test[,4]~test[,3],type="l")

# Example 2. get.transect(), without use of locator(); pretty plot
	par(mfrow=c(2,1),mai=c(1.2, 1, 0.1, 0.1))
	plot(atl, deep=-6000, shallow=-10, step=1000, lwd=0.5, col="grey50",drawlabels=TRUE)
	lines(nw.atlantic.coast)

	get.transect(atl, -75, 44,-46,32, loc=FALSE, dis=TRUE) -> test
	points(test$lon,test$lat,type="l",col="blue",lwd=2,lty=2)
	plotProfile(test)

# Example 3. get.transect(), with use of locator(); pretty plot
if (FALSE) {
	par(mfrow=c(2,1),mai=c(1.2, 1, 0.1, 0.1))
	plot(atl, deep=-6000, shallow=-10, step=1000, lwd=0.5, col="grey50",drawlabels=TRUE)
	lines(nw.atlantic.coast)
	
	get.transect(atl, loc=TRUE, dis=TRUE, col=2, lty=2) -> test
	plotProfile(test)
	}