uniq2nest

This IDL facility turns the Unique Identifier into the corresponding N_side and (NESTED) pixel index.

Location in HEALPix directory tree: src/idl/toolkit/uniq2nest.pro 

FORMAT

IDL> uniq2nest, Puniq, Nside, Pnest [,/HELP]

QUALIFIERS

Puniq

(IN, scalar or vector Integer) The HEALPix Unique pixel identifier(s). Must be $\ge 4$.

Nside

(OUT, same size as Puniq) The HEALPix N_side parameter(s)

Pnest

(OUT, same size as Puniq) (NESTED scheme) pixel identification number(s) over the range {0, 12N_side²-1}.

KEYWORDS

/HELP

If set, a documentation header is printed out, and the routine exits

DESCRIPTION

uniq2nest turns the Unique ID number u = p + 4 N_side², into the parameter N_side (a power of 2) and the pixel index p. See ”The Unique Identifier scheme” section in ”HEALPix Introduction Document” for more details.

EXAMPLE:

uniq2nest, [4,16, 64], nside, pnest
print, nside, pnest

returns
1 2 4
0 0 0
since the pixels with Unique ID numbers 4, 16 and 64 are the first pixels (p=0) at N_side= 1, 2 and 4 respectively.

RELATED ROUTINES

This section lists the routines related to uniq2nest

nest2uniq

Transforms Nside and Nested pixel number into Unique HEALPix pixel ID number

pix2xxx, ...

to turn NESTED pixel index into sky coordinates and back