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query_strip

This IDL facility provides a means to find the index of all pixels belonging to a latitude strip defined by its bounds

FORMAT

IDL> query_strip , Nside, Theta1, Theta2, Listpix, [Nlist, NESTED=, INCLUSIVE=, HELP=]

QUALIFIERS

Nside

HEALPix resolution parameter used to index the pixel list (scalar integer)

Theta1

colatitude lower bound in radians measured from North Pole (between 0 and ).

Theta2

colatitude upper bound in radians measured from North Pole (between 0 and ). If theta1< theta2, the pixels lying in [theta1,theta2] are output, otherwise, the pixel lying in [0, theta2] and those lying in [theta1, ] are output.

Listpix

on output: list of ordered index for the pixels found in the strip. The RING numbering scheme is used unless the keyword NESTED is set. (=-1 if the strip is too small and no pixel is found)

Nlist

on output: number of pixels in Listpix (=0 if no pixel is found).

NESTED =

if set, the output list uses the NESTED numbering scheme instead of the default RING

INCLUSIVE =

if set, all the pixels overlapping (even partially) with the strip are listed, otherwise only those whose center lies within the strip are listed

/HELP

if set, the routine prints its documentation header and exits.

idl

version 6.1 or more is necessary to run query_strip .

ang2pix, pix2ang

conversion between angles and pixel index

vec2pix, pix2vec

conversion between vector and pixel index

query_disc, query_polygon,

query_triangle

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

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EXAMPLE:

query_strip , 256, 0.75*!PI, !PI/5, listpix, nlist, /nest

Returns the NESTED pixel index of all pixels with colatitude in [0,] and those with colatitude in [,]

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Eric Hivon 2010-06-18