healpix_geometry_analysis.coordinates

Healpix tile coordinates math

Classes

HealpixCoordinates

Healpix tile coordinates derived from diagonal indices

Module Contents

class HealpixCoordinates

Healpix tile coordinates derived from diagonal indices

Parameters:

nside (int) – Healpix nside parameter, 2^order

grid: healpix_geometry_analysis.grid.HealpixGrid

Healpix grid object specifying order

classmethod from_order(order: int) → Self

Create HealpixCoordinates using healpix order (depth)

classmethod from_nside(nside: int) → Self

Create HealpixCoordinates using Nside parameter

xyz(k, kp)

Cartesian coordinates on the unit sphere from diagonal indices

Parameters:

• k (float) – NW-SE diagonal index

• kp (float) – NE-SW diagonal index

Returns:

• x (float) – Cartesian x coordinate

• y (float) – Cartesian y coordinate

• z (float) – Cartesian z coordinate

lonlat_radians(k, kp)

Longitude and latitude in radians from diagonal indices

Parameters:

• k (float) – SW-NE diagonal index

• kp (float) – SE-NW diagonal index

Returns:

• lon (float) – Longitude in radians

• lat (float) – Latitude in radians

lonlat_degrees(k, kp)

Longitude and latitude in degrees from diagonal indices

Parameters:

• k (float) – NW-SE diagonal index

• kp (float) – NE-SW diagonal index

Returns:

• lon (float) – Longitude in degrees

• lat (float) – Latitude in degrees

phi_z(k, kp)

Cylindrical coordinates from diagonal indices

Parameters:

• k (float) – NW-SE diagonal index

• kp (float) – NE-SW diagonal index

Returns:

• phi (float) – Longitude in radians

• z (float) – Sine of the latitude

_eq(k, kp)

Cylidrical coordinates assuming the equatorial region

_polar(k, kp)

Cylindrical coordinates assuming the polar region

cos_arc(k1, kp1, k2, kp2)

Cosine of the great circle arc between two pixels

chord_squared(k1, kp1, k2, kp2)

Square of chord distance between two pixels

diag_from_phi_z(phi: HealpixCoordinates.diag_from_phi_z.T, z: HealpixCoordinates.diag_from_phi_z.T) → tuple[HealpixCoordinates.diag_from_phi_z.T, HealpixCoordinates.diag_from_phi_z.T]

Diagonal indices from cylindrical coordinates

_diag_eq(phi: HealpixCoordinates._diag_eq.T, z: HealpixCoordinates._diag_eq.T) → tuple[HealpixCoordinates._diag_eq.T, HealpixCoordinates._diag_eq.T]

Diagonal indices assuming the equatorial region

_diag_pol(phi: HealpixCoordinates._diag_pol.T, z: HealpixCoordinates._diag_pol.T) → tuple[HealpixCoordinates._diag_pol.T, HealpixCoordinates._diag_pol.T]

Diagonal indices assuming the polar region

diag_from_lonlat_degrees(lon: HealpixCoordinates.diag_from_lonlat_degrees.T, lat: HealpixCoordinates.diag_from_lonlat_degrees.T) → tuple[HealpixCoordinates.diag_from_lonlat_degrees.T, HealpixCoordinates.diag_from_lonlat_degrees.T]

Diagonal indices from longitude and latitude in degrees

Parameters:

• lon (float) – Longitude in degrees

• lat (float) – Latitude in degrees

Returns:

• k (float) – NW-SE diagonal index

• kp (float) – NE-SW diagonal index