query_strip

Routine to find the index of all pixels enclosed in a latitude strip. 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_strip( nside, theta1, theta2, listpix, nlist[, nest, inclusive] )

ARGUMENTS

name&dimensionality	kind	in/out	description
nside	I4B	IN	the $N_{\mathrm{side}}$ parameter of the map.
theta1	DP	IN	colatitude lower bound in radians measured from North Pole (between 0 and $\pi$).
theta2	DP	IN	colatitude upper bound in radians measured from North Pole (between 0 and $\pi$). If theta1$<$ theta2, the pixels lying in [theta1,theta2] are output, otherwise, the pixel lying in [0, theta2] and those lying in [theta1, $\pi$] are output.
listpix(0:*)	I4B/ I8B	OUT	the index for all pixels enclosed in the strip(s). 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 strip are listed; otherwise only those whose center lies within the strip are listed.

EXAMPLE:

call query_strip(256,0.75*PI,0.2*PI,listpix,nlist,nest=1)

Returns the NESTED pixel index of all pixels with colatitude in [0,$\pi/5$] and those with colatitude in [$3\pi/4$,$\pi$]

MODULES & ROUTINES

This section lists the modules and routines used by query_strip.

in_ring

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

intrs_intrv

routine to compute the intersection of 2 intervals on a circle

ring_num

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

vect_prod

routine to compute the vectorial product of two 3D vectors

RELATED ROUTINES

This section lists the routines related to query_strip

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