rgdal (version 0.8-13)

project: Projection of coordinate matrices

Description

Interface to the PROJ.4 library of projection functions for geographical position data, no datum transformation possible. Use spTransform() for extended support.

Usage

project(xy, proj, inv = FALSE, use_ob_tran=FALSE)

Arguments

xy

2-column matrix of coordinates

proj

character string of projection arguments; the arguments must be entered exactly as in the PROJ.4 documentation, in particular there cannot be any white space in += strings, and successive such strings can only be separated by blanks.

inv

default FALSE, if TRUE inverse projection to geographical coordinates

use_ob_tran

default FALSE, if TRUE and +proj=ob_tran, use General Oblique Transformation with internalised from/to projection reversal; the user oblique transforms forward rather than inverse.

Value

• A two column matrix with projected coordinates.

Details

Full details of projection arguments available from website below, and examples in file "epsg" in the data directory installed with PROJ.4.

References

http://proj.maptools.org/

See Also

CRS-class, spTransform-methods

Examples

data(state)
res <- project(cbind(state.center$x, state.center$y),
 "+proj=lcc +lat_1=48 +lat_2=33 +lon_0=-100")
res1 <- project(res, "+proj=lcc +lat_1=48 +lat_2=33 +lon_0=-100", inv=TRUE)
summary(res1 - cbind(state.center$x, state.center$y))
plot(cbind(state.center$x, state.center$y), asp=1, type="n")
text(cbind(state.center$x, state.center$y), state.abb)
plot(res, asp=1, type="n")
text(res, state.abb)
crds <- matrix(data=c(9.05, 48.52), ncol=2)
a <- project(crds, paste("+proj=ob_tran +o_proj=longlat",
 "+o_lon_p=-162 +o_lat_p=39.25 +lon_0=180 +ellps=sphere +no_defs"),
 use_ob_tran=TRUE)
a
#should be (-5.917698, -1.87195)
project(a, paste("+proj=ob_tran +o_proj=longlat",
 "+o_lon_p=-162 +o_lat_p=39.25 +lon_0=180 +ellps=sphere +no_defs"),
 inv=TRUE, use_ob_tran=TRUE)

#added after posting by Martin Ivanov