Creates either a CRS object or an inla.CRS object, describing a coordinate reference system
Usage
fm_CRS(...)
# S3 method for crs
fm_CRS(x, ...)
# S3 method for fm_crs
fm_CRS(x, ...)
# S3 method for Spatial
fm_CRS(x, ...)
# S3 method for inla.CRS
fm_CRS(x, ..., crsonly = FALSE)
# S3 method for sf
fm_CRS(x, ..., crsonly = FALSE)
# S3 method for sfc
fm_CRS(x, ..., crsonly = FALSE)
# S3 method for sfg
fm_CRS(x, ..., crsonly = FALSE)
# S3 method for inla.mesh
fm_CRS(x, ..., crsonly = FALSE)
# S3 method for inla.mesh.lattice
fm_CRS(x, ..., crsonly = FALSE)
# S3 method for inla.segment
fm_CRS(x, ..., crsonly = FALSE)
# S3 method for CRS
fm_CRS(x, oblique = NULL, ...)
# S3 method for default
fm_CRS(
projargs = NULL,
doCheckCRSArgs = TRUE,
args = NULL,
oblique = NULL,
SRS_string = NULL,
...
)
Arguments
- ...
Additional parameters. Not currently in use.
- x
Object to convert to CRS or to extract CRS information from.
- crsonly
logical; if
TRUE
, remove any obliqueinformation for
inla.CRSclass objects and return a pure
CRSclass object. Default:
FALSE`.- oblique
Vector of length at most 4 of rotation angles (in degrees) for an oblique projection, all values defaulting to zero. The values indicate (longitude, latitude, orientation, orbit), as explained in the Details section below.
- projargs
Either 1) a projection argument string suitable as input to
sp::CRS
, or 2) an existingCRS
object, or 3) a shortcut reference string to a predefined projection; runnames(fm_wkt_predef())
for valid predefined projections.- doCheckCRSArgs
default TRUE, must be set to FALSE by package developers including
CRS
in an S4 class definition to avoid uncontrollable loading of thergdal
namespace.- args
An optional list of name/value pairs to add to and/or override the PROJ4 arguments in
projargs
.name=value
is converted to"+name=value"
, andname=NA
is converted to"+name"
.- SRS_string
a WKT2 string defining the coordinate system; see
sp::CRS
. This takes precedence overprojargs
.
Value
Either an sp::CRS
object or an inla.CRS
object,
depending on if the coordinate reference system described by the parameters
can be expressed with a pure sp::CRS
object or not.
An S3 inla.CRS
object is a list, usually (but not necessarily)
containing at least one element:
- crs
The basic
sp::CRS
object
Details
The first two
elements of the oblique
vector are the (longitude, latitude)
coordinates for the oblique centre point. The third value (orientation) is a
counterclockwise rotation angle for an observer looking at the centre point
from outside the sphere. The fourth value is the quasi-longitude (orbit
angle) for a rotation along the oblique observers equator.
Simple oblique: oblique=c(0, 45)
Polar: oblique=c(0, 90)
Quasi-transversal: oblique=c(0, 0, 90)
Satellite orbit viewpoint: oblique=c(lon0-time*v1, 0, orbitangle, orbit0+time*v2)
, where lon0
is the longitude at which a satellite
orbit crosses the equator at time=0
, when the satellite is at an
angle orbit0
further along in its orbit. The orbital angle relative
to the equatorial plane is orbitangle
, and v1
and v2
are the angular velocities of the planet and the satellite, respectively.
Note that "forward" from the satellite's point of view is "to the right" in
the projection.
When oblique[2]
or oblique[3]
are non-zero, the resulting
projection is only correct for perfect spheres.
Author
Finn Lindgren finn.lindgren@gmail.com