epi.circle {ssBase}R Documentation

Calculate Epicentral Coordinates of a Circle

Description

Calculates the epicentral coordinates of 399 points on the perimeter of a circle of given radius centred at (centrelong, centrelat). The circle radius is the arc length radius on the surface of the earth.

Usage

epi.circle(centrelong, centrelat, radius, earthradius=6371)

Arguments

centrelong a number specifying the longitude in degrees of the circle centre.
centrelat a number specifying the latitude in degrees of the circle centre.
radius a number specifying the circle radius in kilometres.
earthradius assumed radius of the earth in kilometres. The default is 6371 km.

Value

If the function call is assigned to another object, then a list object is returned. It contains the following components.

centrelong as specified above.
centrelat as specified above.
radius as specified above.
longitude a vector giving the longitude of 399 points on the circle perimeter.
latitude a vector giving the latitude of 399 points on the circle perimeter.

Author(s)

Yang Wenzheng, 1998

Examples

x <- epi.circle(175, -42, 3000)

#   Now project the circle outline
y <- projection(6371, x$latitude, x$longitude, 175, -42)
par(pin=c(5,5))
plot(y$x, y$y, type="l")
[Package ssBase version 2.2-1 Index]