destPoint: Destination given bearing (direction) and distance

Description Usage Arguments Value Note Author(s) References Examples

View source: R/destPoint.R

Description

Given a start point, initial bearing (direction), and distance, this function computes the destination point travelling along a the shortest path on an ellipsoid (the geodesic).

Usage

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destPoint(p, b, d, a=6378137, f=1/298.257223563, ...)

Arguments

p

Longitude and Latitude of point(s), in degrees. Can be a vector of two numbers, a matrix of 2 columns (first one is longitude, second is latitude) or a SpatialPoints* object

b

numeric. Bearing (direction) in degrees

d

numeric. Distance in meters

a

major (equatorial) radius of the ellipsoid. The default value is for WGS84

f

ellipsoid flattening. The default value is for WGS84

...

additional arguments. If an argument 'r' is supplied, this is taken as the radius of the earth (e.g. 6378137 m) and computations are for a sphere (great circle) instead of an ellipsoid (geodetic). This is for backwards compatibility only

Value

A pair of coordinates (longitude/latitude)

Note

Direction changes continuously when travelling along a geodesic. Therefore, the final direction is not the same as the initial direction. You can compute the final direction with finalBearing (see examples, below)

Author(s)

This function calls GeographicLib code by C.F.F. Karney

References

C.F.F. Karney, 2013. Algorithms for geodesics, J. Geodesy 87: 43-55. https://dx.doi.org/10.1007/s00190-012-0578-z. Addenda: http://geographiclib.sf.net/geod-addenda.html. Also see http://geographiclib.sourceforge.net/

Examples

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p <- cbind(5,52)
d <- destPoint(p,30,10000)
d

#final direction, when arriving at endpoint: 
finalBearing(d, p)

Example output

Loading required package: sp
         lon      lat
[1,] 5.07293 52.07781
[1] -150

geosphere documentation built on July 21, 2018, 3 p.m.