maptools (version 1.0-1)

gcDestination: Find destination in geographical coordinates

Description

Find the destination in geographical coordinates at distance dist and for the given bearing from the starting point given by lon and lat.

Usage

gcDestination(lon, lat, bearing, dist, dist.units = "km",
 model = NULL, Vincenty = FALSE)

Arguments

lon

longitude (Eastings) in decimal degrees (either scalar or vector)

lat

latitude (Northings) in decimal degrees (either scalar or vector)

bearing

bearing from 0 to 360 degrees (either scalar or vector)

dist

distance travelled (scalar)

dist.units

units of distance "km" (kilometers), "nm" (nautical miles), "mi" (statute miles)

model

choice of ellipsoid model ("WGS84", "GRS80", "Airy", "International", "Clarke", "GRS67"

Vincenty

logical flag, default FALSE

Value

A matrix of decimal degree coordinates with Eastings in the first column and Northings in the second column.

Details

The bearing argument may be a vector when lon and lat are scalar, representing a single point.

References

http://www.movable-type.co.uk/scripts/latlong.html#ellipsoid,

the file earlier available at http:\/\/williams.best.vwh.net/avform.htm,

http://www.movable-type.co.uk/scripts/latlong-vincenty-direct.html,

Original reference http://www.ngs.noaa.gov/PUBS_LIB/inverse.pdf:

Vincenty, T. 1975. Direct and inverse solutions of geodesics on the ellipsoid with application of nested equations. Survey Review 22(176):88-93

See Also

gzAzimuth

Examples

# NOT RUN {
data(state)
res <- gcDestination(state.center$x, state.center$y, 45, 250, "km")
plot(state.center$x, state.center$y, asp=1, pch=16)
arrows(state.center$x, state.center$y, res[,1], res[,2], length=0.05)
llist <- vector(mode="list", length=length(state.center$x))
for (i in seq(along=llist)) llist[[i]] <- gcDestination(state.center$x[i],
  state.center$y[i], seq(0, 360, 5), 250, "km")
plot(state.center$x, state.center$y, asp=1, pch=3)
nll <- lapply(llist, lines)
# }