GLCP pixelization      

ECP pixelization:

It is a version of the ECP pixelization (or rather discretization) scheme as described in Mucciacia, Natoli, & Vittorio, 1997. The S2HAT pixelization structure, pixelization, of the type s2hat_pixeltype, describing this scheme is set by calling

set_pixelization( PIXCHOICE_ECP, pixpars, pixelization),

where PIXCHOICE_ECP is a predefined S2HAT parameter (a 4-byte integer set to 2) and
the field par1 of the pixpars variable is equal to nrings, i.e., a total number of iso-latitude rings
the field par2 of the pixpars variable is equal to nphi, i.e., a number of pixels per ring.

Check here or here to find more about the set_pixelization routine in Fortran 90 and C, respectively.

Brief description

The pixel centers are located on the iso-latitude rings given by,

theta_i = dtheta/2 + i dtheta, for i = 0, ..., nrings-1 and dtheta = PI/nrings

and for each latitude their azimuths are given by,

phi_j = j dphi, for j = 0, ..., nphi-1 and dphi = 2 PI/nphi.

The global numbering scheme starts with a pixel 0 at the North Pole and goes ring-by-ring, left-to-right.