project.lonlat.to.M3: Project coordinates from longitude/latitude to model units.
In M3: Reading M3 files

Description Usage Arguments Details Value Author(s) References See Also Examples

Project coordinates from longitude/latitude to model units as specified according to the projection given by a user-designated Models3-formatted file.

1	project.lonlat.to.M3(longitude, latitude, file, units, ...)

`longitude`	Vector of longitudes for the points to be projected.
`latitude`	Vector of latitudes for the points to be projected.
`file`	File name of Models3-formatted file which contains information about the projection to which you want `x` and `y` to be projected.
`units`	Units in which to return `x` and `y`. Options are "km" or "m", with "km" as the default.
`...`	Other arguments to pass to `get.proj.info.M3` function. In this case, the only relevant argument would be the earth radius to use for the projection in `file`.

This function uses the function project from the package rgdal to project from longitude/latitude to the projection defined by the Models3-formatted file. Package rgdal provides the R interface to GDAL (Geospatial Data Abstraction Library, http://www.gdal.org).

A list containing the elements coords and units. The element coords contains a matrix of coordinates using the projection in file. The element units contains the units of the coordinates, as specifed by units or "km" by default.

Jenise Swall

http://www.gdal.org

project.M3.to.lonlat, project.M3.1.to.M3.2, get.proj.info.M3

## List of state capital longitudes/latitudes
## (from http://www.xfront.com/us_states).
capitals <- data.frame(x=c(-84.39,-86.28,-81.04,-86.78,-78.64,-84.86),
                       y=c(33.76,32.36,34.00,36.17,35.77,38.20),
                       name=c("Atlanta", "Montgomery", "Columbia",
                                 "Nashville", "Raleigh", "Frankfort")
                        )
## Plot these on a map, with state lines.
plot(capitals$x, capitals$y)
map("state", add=TRUE)

## Now, put these on the same Lambert conic conformal projection used
## in the demo file below.
lcc.file <- system.file("extdata/ozone_lcc.ncf", package="M3")
lcc.capitals <- project.lonlat.to.M3(capitals$x, capitals$y, lcc.file)

## Put these on a new plot.
dev.new()
plot(lcc.capitals$coords)
## Project state lines to this projection.
lcc.map <- get.map.lines.M3.proj(lcc.file)
lines(lcc.map$coords)