Enum Projection 

pub enum Projection {
    Linear,
    Gnomonic,
    Orthographic,
    Stereographic,
    ZenithalEquidistant,
    ZenithalEqualArea,
    PlateCarree,
    Mercator,
    CylindricalEqualArea,
    HammerAitoff,
    Mollweide,
}

How a flat image plane is carried onto the celestial sphere.

The projection is named by the last three characters of CTYPEn, after the coordinate type and a hyphen — RA---TAN is right ascension under the gnomonic projection.

Each projection converts between the intermediate world coordinates the header’s matrix produces and the native spherical coordinates of the projection’s own frame; Wcs then rotates those onto the sky. A point the projection cannot represent — the far hemisphere under TAN, say — comes back as NaN rather than as a plausible coordinate in the wrong place.

Variants

Linear

No projection code: the intermediate coordinates are the world coordinates, offset from the reference value. This is what a plain LINEAR, PIXEL or wavelength axis uses.

Gnomonic

TAN, the gnomonic projection. Straight lines on the sky stay straight on the plane, which is what an ordinary telescope with a flat detector produces, and by far the most common projection in astronomy images.

Orthographic

SIN, the orthographic projection: the sphere as seen from infinitely far away. Radio interferometers image in it.

Stereographic

STG, the stereographic projection, which preserves angles.

ZenithalEquidistant

ARC, the zenithal equidistant projection, where radius from the reference point is the angle from it. Schmidt plates and many all-sky cameras use it.

ZenithalEqualArea

ZEA, the zenithal equal-area projection, which preserves area.

PlateCarree

CAR, the plate carrée: longitude and latitude used directly as rectangular coordinates.

Mercator

MER, the Mercator projection.

CylindricalEqualArea

CEA, the cylindrical equal-area projection, whose standard parallel is set by PV2_1.

HammerAitoff

AIT, the Hammer-Aitoff projection, an equal-area whole-sky projection. All-sky maps are usually drawn in it.

Mollweide

MOL, the Mollweide projection, another equal-area whole-sky one.

Implementations

impl Projection

pub fn from_ctype(ctype: &str) -> Result<Self, Box<dyn Error + Send + Sync>>

Reads the projection out of a CTYPEn card.

Errors

Returns an error for a projection this crate does not implement, rather than silently falling back to a linear mapping — a wrong projection yields plausible coordinates that are quietly in the wrong place.

pub fn code(self) -> &'static str

The projection’s three-letter code, or LINEAR for no projection at all.

Trait Implementations

impl Clone for Projection

fn clone(&self) -> Projection

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for Projection

impl Debug for Projection

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Eq for Projection

impl PartialEq for Projection

fn eq(&self, other: &Projection) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for Projection