This IDL facility provides a means to find the index of all pixels belonging to
a sperical triangle defined by its vertices
Location in HEALPix directory tree:
query_triangle , Nside, Vector1, Vector2, Vector3, Listpix, [Nlist, NESTED=, INCLUSIVE=]
- HEALPix resolution parameter used to index the pixel list (scalar integer)
- 3D cartesian position vector of the triangle first vertex
- 3D cartesian position vector of the triangle second vertex
- 3D cartesian position vector of the triangle third vertex
NB : the norm of Vector* does not have to be one, what is
considered is the intersection of the sphere with the line of
- on output: list of ordered index for the pixels found
in the triangle. The RING numbering scheme is used unless the keyword NESTED is set.
(=-1 if the triangle is too small and no pixel is found)
- on output: number of pixels in Listpix (=0 if no pixel is found).
- if set, the output list uses the NESTED numbering scheme
instead of the default RING
- if set, all the pixels overlapping (even partially)
with the triangle are listed, otherwise only those whose
center lies within the triangle are listed
query_triangle finds the pixels within the given triangle in a selective way WITHOUT
scanning all the sky pixels. The numbering scheme of the output list and the
inclusiveness of the triangle can be changed
This section lists the routines related to query_triangle
- version 6.1 or more is necessary to run query_triangle .
- conversion between angles and pixel index
- conversion between vector and pixel index
- render the list of pixels enclosed
respectively in a given disc, polygon, latitude strip and triangle
On return listpix contains the index of the (98560) pixels lying in the octant
The pixel indices correspond to the RING scheme with resolution 256.