omerc: Oblique Mercator, Cylindrical, and Mollweide projections

Description

Defines an appropriate Oblique Mercator, Oblique Cylindrical Equal Area, and Mollweide projections for a supplied Spatial object

Usage

omerc(x, angle,  
	post=c('none', 'north', 'wide','tall'),
    preserve=NULL, ellipse=TRUE) 
    ocea(x, angle, flip=FALSE)
    moll(x=0, angle=NULL, flip=FALSE)

Value

An object of class crs.

Arguments

x: A SpatVector object or a vector of length 2 giving the centroid of the projection.
angle: angle of rotation or vector of angles
post: post-projection angle rotation
flip: post-projection flipping of coordinates
preserve: A SpatVector object, the resulting projection is scaled so as to preserve the distances between these points as best as possible.
ellipse: compute projection region and areas to crop when projecting.

Details

With omerc, an Oblique Mercator map projection is produced which warps the world onto a cylinder, with the north-south axis rotated by the specified angle. If angle is a vector, the optimal angle for reducing the size of the bounding box is returned.

If post = 'north', an inverse rotation will preserve the north direction at the origin.

If post = 'wide', an inverse rotation makes the smallest possible bounding box which is wider than tall.

If post = 'tall', the bounding box is taller than it is wide

If post is numeric, it specifies an angle for inverse rotation.

ocea produces an Oblique Cylindrical Equal Area projection and moll a Mollweide projections

References

https://en.wikipedia.org/w/index.php?title=Space-oblique_Mercator_projection

Examples

Run this code


data('worldMap')
worldMap = terra::unwrap(worldMap)


myProj = omerc(c(-100,-70), angle=-45)
crs(myProj, proj=TRUE)

plot(project(worldMap, crsLL))
plot(attributes(myProj)$crop, col='red', add=TRUE)

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