1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
|
\name{gcDestination}
\alias{gcDestination}
%- Also NEED an '\alias' for EACH other topic documented here.
\title{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)
}
%- maybe also 'usage' for other objects documented here.
\arguments{
\item{lon}{longitude (Eastings) in decimal degrees (either scalar or vector)}
\item{lat}{latitude (Northings) in decimal degrees (either scalar or vector)}
\item{bearing}{bearing from 0 to 360 degrees (either scalar or vector)}
\item{dist}{distance travelled (scalar)}
\item{dist.units}{units of distance "km" (kilometers), "nm" (nautical miles), "mi" (statute miles)}
\item{model}{choice of ellipsoid model ("WGS84", "GRS80", "Airy", "International", "Clarke", "GRS67"}
\item{Vincenty}{logical flag, default FALSE}
}
\details{
The bearing argument may be a vector when lon and lat are scalar, representing a single point.
}
\value{
A matrix of decimal degree coordinates with Eastings in the first column and Northings in the second column.
}
\references{\url{http://www.movable-type.co.uk/scripts/latlong.html#ellipsoid},
the file earlier available at \code{http:\/\/williams.best.vwh.net/avform.htm},
\url{http://www.movable-type.co.uk/scripts/latlong-vincenty-direct.html},
Original reference \url{https://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}
\author{Eric Archer and Roger Bivand}
\seealso{\code{\link{gzAzimuth}}}
\examples{
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)
}
% Add one or more standard keywords, see file 'KEYWORDS' in the
% R documentation directory.
\keyword{spatial}
|
