query_disc

Routine to find the index of all pixels within an angular distance radius from a defined center. The output indices can be either in the RING or NESTED scheme

Location in HEALPix directory tree: src/f90/mod/pix_tools.F90 

FORMAT

call query_disc( nside, vector0, radius, listpix, nlist[, nest, inclusive] )

ARGUMENTS

name & dimensionality	kind	in/out	description
nside	I4B	IN	the $N_{\mathrm{side}}$ parameter of the map.
vector0(3)	DP	IN	cartesian vector pointing at the disc center.
radius	DP	IN	disc radius in radians.
listpix(0:*)	I4B/ I8B	OUT	the index for all pixels within radius. Make sure that the size of the array is big enough to contain all pixels.
nlist	I4B/ I8B	OUT	The number of pixels listed in listpix.
nest (OPTIONAL)	I4B	IN	The pixel indices are in the NESTED numbering scheme if nest=1, and in RING scheme otherwise.
inclusive (OPTIONAL)	I4B	IN	If set to 1, all the pixels overlapping (even partially) with the disc are listed, otherwise only those whose center lies within the disc are listed.

EXAMPLE:

use healpix_modules
call query_disc(256,(/0,0,1/),pi/2,listpix,nlist,nest=1)

Returns the NESTED pixel index of all pixels north of the equatorial line in a $N_{\mathrm{side}}=256$ map.

MODULES & ROUTINES

This section lists the modules and routines used by query_disc.

in_ring

routine to find the pixels in a certain slice of a given ring.

ring_num

function to return the ring number corresponding to the coordinate $z$

RELATED ROUTINES

This section lists the routines related to query_disc

pix2ang, ang2pix

convert between angle and pixel number.

pix2vec, vec2pix

convert between a cartesian vector and pixel number.

query_disc, query_polygon,

query_strip, query_triangle

render the list of pixels enclosed respectively in a given disc, polygon, latitude strip and triangle

surface_triangle

computes the surface in steradians of a spherical triangle defined by 3 vertices