project.M3.1.to.M3.2: Project coordinates based on projection in the first file to...

In M3: Reading M3 files

Description

Project coordinates based on projection in the first Models3-formatted file to the projection given in the second Models3-formatted file.

Usage

project.M3.1.to.M3.2(x, y, from.file, to.file, units, ...)

Arguments

x	x-coordinates in model units from projection in first file
y	y-coordinates in model units from projection in first file
from.file	Name of Models3-formatted file with the same model projection as x and y. These coordinates will be re-projected to the projection given in file2.
to.file	Name of Models3-formatted file with the model projection to which you want x and y to be projected.
units	Units of x and y. The coordinates returned will also be in these units.
...	Other arguments to pass to get.proj.info.M3 function. In this case, the only relevant argument would be the earth radius to use when doing the projections.

Details

This function calls get.proj.info.M3 which reads the projection information (using the package ncdf4) and transforms it to strings that are understood by functions in rgdal. Package rgdal provides the R interface to GDAL (Geospatial Data Abstraction Library, http://www.gdal.org).

Value

A list containing the elements coords and units. The element coords contains a matrix of coordinates using projection in to.file. The element units contains the units of the coordinates, which are the same as those specified for input x and y.

Warning

This function assumes the projections in from.file and to.file are Lambert conic conformal or polar stereographic.

Author(s)

Jenise Swall

References

http://www.gdal.org

See Also

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

Examples

## Find the path to a demo file with lambert conic conformal projection.
lcc.file <- system.file("extdata/ozone_lcc.ncf", package="M3")

## Read in the ozone for July 4 for eastern U.S.
lcc.oz <- get.M3.var(file=lcc.file, var="O3",
                      lcol=90, ucol=130, lrow=30, urow=80,
                      ldatetime=as.Date("2001-07-04"),
                      udatetime=as.Date("2001-07-04"))

## Get the cell centers for this subset.
east.ctrs <- expand.grid(lcc.oz$x.cell.ctr, lcc.oz$y.cell.ctr)
plot(east.ctrs, cex=0.3, xlab="x", ylab="y")

## Find map lines on this projection, superplot.
lcc.state.bds <- get.map.lines.M3.proj(file=lcc.file)$coords
lines(lcc.state.bds, col="darkblue")


## Find the path to a demo file with polar stereographic projection.
polar.file <- system.file("extdata/surfinfo_polar.ncf", package="M3")

## Put the cell centers from the subsetted ozone data on this polar
## stereographic projection.
polar.oz <- project.M3.1.to.M3.2(east.ctrs[,1], east.ctrs[,2],
                                 from.file=lcc.file,
                                 to.file=polar.file,
                                 units=lcc.oz$hz.units)

## Plot the cells centers and boundary lines on the polar
## stereographic projection.
dev.new()
plot(polar.oz$coords)
polar.state.bds <- get.map.lines.M3.proj(file=polar.file)$coords
lines(polar.state.bds, col="darkblue")

M3 documentation built on May 2, 2019, 11:04 a.m.