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diff --git a/docs/source/operations/projections/healpix.rst b/docs/source/operations/projections/healpix.rst new file mode 100644 index 00000000..d05b2123 --- /dev/null +++ b/docs/source/operations/projections/healpix.rst @@ -0,0 +1,55 @@ +.. _healpix: + +******************************************************************************** +HEALPix +******************************************************************************** ++---------------------+----------------------------------------------------------+ +| **Classification** | Mixed | ++---------------------+----------------------------------------------------------+ +| **Available forms** | Forward and inverse, spherical and elliptical projection | ++---------------------+----------------------------------------------------------+ +| **Defined area** | Global | ++---------------------+----------------------------------------------------------+ +| **Implemented by** | Alex Raichev and Michael Speth | ++---------------------+----------------------------------------------------------+ +| **Options** | ++---------------------+----------------------------------------------------------+ +| `No special options for this projection` | ++---------------------+----------------------------------------------------------+ + +.. image:: ../../../images/healpix.png + :scale: 75% + :alt: HEALPix + +The HEALPix projection is area preserving and can be used with a spherical and +ellipsoidal model. It was initially developed for mapping cosmic background +microwave radiation. The image below is the graphical representation of the +mapping and consists of eight isomorphic triangular interrupted map graticules. +The north and south contains four in which straight meridians converge polewards +to a point and unequally spaced horizontal parallels. HEALPix provides a mapping +in which points of equal latitude and equally spaced longitude are mapped to points +of equal latitude and equally spaced longitude with the module of the polar +interruptions. + + +Usage +############################################################################### + +To run a forward HEALPix projection on a unit sphere model, use the following command:: + + proj +proj=healpix +lon_0=0 +a=1 -E <<EOF + 0 0 + EOF + # output + 0 0 0.00 0.00 + +Further reading +################################################################################ + +#. `NASA <http://healpix.jpl.nasa.gov/>`_ +#. `Wikipedia <https://en.wikipedia.org/wiki/HEALPix>`_ + + + + + |