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 ${N_{\rm side}}$ 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 ${N_{\rm side}}=256$ 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

Version 3.31, 2017-01-06