crs

crs

Planetary coordinate reference systems via IAU codes.

Thin, pyproj-only helpers that resolve IAU planetary CRS and build feature-centered local projections. The body’s ellipsoid / radii are carried by the IAU code itself — nothing is looked up or hardcoded here.

PROJ ships a single IAU CRS edition (IAU_2015); there is no IAU_2009/IAU_2006/… authority, so everything here builds against IAU_2015. (This is unrelated to :mod:planetarypy.constants, which does carry multiple IAU PCK editions for body parameters.)

Body names are resolved to NAIF ids via :mod:planetarypy.constants (one shared body registry); pass a NAIF id integer to skip that import. On a fresh install, the first name resolution triggers the one-time NSSDC archive download that planetarypy.constants performs.

Examples

>>> from planetarypy.crs import body_crs, local_crs
>>> body_crs("mars")                   # Mars ocentric geographic CRS
>>> body_crs(499, system="ographic")   # by NAIF id
>>> local_crs(137.4, -4.6, "mars")     # azeqd centered on Gale crater

Functions

Name	Description
body_crs	Return a body’s geographic CRS from the IAU 2015 authority.
get_crs	craterpy-compatible alias for :func:body_crs.
local_crs	Azimuthal-Equidistant CRS centered on (lon, lat) for body.

body_crs

crs.body_crs(body, system='ocentric')

Return a body’s geographic CRS from the IAU 2015 authority.

Parameters

Name	Type	Description	Default
body	str or int	Body name (resolved via :mod:planetarypy.constants) or NAIF id.	required
system	(ocentric, ographic)	Latitude convention. "ocentric" (the spherical IAU definition) is available for every body; "ographic" only for bodies that define it (e.g. Mars, Jupiter — not the Moon or Vesta).	"ocentric"

Returns

Name	Type	Description
	pyproj.CRS	The ellipsoid/radii come from the IAU code itself.

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get_crs

crs.get_crs(body, system='default')

craterpy-compatible alias for :func:body_crs.

system="default" maps to "ocentric". Unlike craterpy’s original, this does NOT accept an arbitrary CRS string as system (no exception-driven passthrough) — construct such CRS with pyproj directly.

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local_crs

crs.local_crs(lon, lat, body, *, system='ocentric')

Azimuthal-Equidistant CRS centered on (lon, lat) for body.

Built on the body’s IAU geodetic CRS, so its sphere/ellipsoid comes from the IAU code (nothing looked up). Use for feature-centered work — local buffering, annulus geometry, distance-true measurements near the center.

Parameters

Name	Type	Description	Default
lon	float	Center longitude/latitude in degrees.	required
lat	float	Center longitude/latitude in degrees.	required
body	str or int	Body name or NAIF id.	required
system	str	See :func:body_crs.	'ocentric'

Returns

Name	Type	Description
	pyproj.CRS	A projected CRS (metres) centered on the given point.

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