xy2pix

Find (nest indexed) MEALPix pixel number corresponding to a pixel index on a HEALPix face

Contents

Syntax

ipix = xy2pix(nSide, ix, iy, nFace)

Input Arguments

nside     HEALPix resolution parameter (power of 2)
ix,iy     integer pixel location on face (1 <= ix, iy <= nSide)
nFace     HEALPix face  number (1 <= nFace <= 12)

One or both ix and iy may be scalars. If neither is a scalar both must have the same size.

Return Arguments

ipix      NESTED pixel index for given x,y on the face

Description

At lowest resolution HEALPix divides the sphere into 12 faces, each with its own coordinate system. Each face is further subdivided in a regular fashion as the resolution parameter is increased. Given a face number (from 1 to 12), a resolution parameter, and a location on the face XY2PIX identifies the pixel number (in the nested indexing scheme).

Example

nSide = 4;
nFace = 3;
ix = [1 2; 1 2];
iy = [1 1; 2 2];
nPix = xy2pix(nSide,ix,iy,nFace)
nPix =

    49    50
    51    52

See also

pix2xy

Copyright 2010-2011 Lee Samuel Finn. Terms of Use.