Create a coordinate reference system object
Creates either a CRS object or an inla.CRS object, describing a coordinate reference system
fm_CRS( projargs = NULL, doCheckCRSArgs = TRUE, args = NULL, oblique = NULL, SRS_string = NULL, ... ) fm_wkt_predef()
projargs |
Either 1) a projection argument string suitable as input to
|
doCheckCRSArgs |
default TRUE, must be set to FALSE by package
developers including |
args |
An optional list of name/value pairs to add to and/or override
the PROJ4 arguments in |
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. |
SRS_string |
a WKT2 string defining the coordinate system;
see |
... |
Additional parameters. Not currently in use. |
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.
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 |
fm_wkt_predef returns a WKT2 string defining a projection
Finn Lindgren finn.lindgren@gmail.com
if (require(rgdal)) {
if (fm_has_PROJ6()) {
crs1 <- fm_CRS("longlat_globe")
crs2 <- fm_CRS("lambert_globe")
crs3 <- fm_CRS("mollweide_norm")
crs4 <- fm_CRS("hammer_globe")
crs5 <- fm_CRS("sphere")
crs6 <- fm_CRS("globe")
} else {
# Old definitions for pre-PROJ6:
# Old radius-1 projections have a added "_norm" in the PROJ6 version of
# the fm_CRS() predefined projections. They are detected and converted
# to the new versions when RPOJ6 is available.
crs1 <- fm_CRS("longlat") # PROJ6: longlat_norm
crs2 <- fm_CRS("lambert") # PROJ6: lambert_norm
crs3 <- fm_CRS("mollweide") # PROJ6: mollweide_norm
crs4 <- fm_CRS("hammer") # PROJ6: hammer_norm
crs5 <- fm_CRS("sphere")
crs6 <- fm_CRS("globe")
}
}
## Not run:
names(fm_wkt_predef())
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