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| -rw-r--r-- | docs/source/projections/healpix.rst | 51 |
1 files changed, 48 insertions, 3 deletions
diff --git a/docs/source/projections/healpix.rst b/docs/source/projections/healpix.rst index 093ae968..885ea3ea 100644 --- a/docs/source/projections/healpix.rst +++ b/docs/source/projections/healpix.rst @@ -3,8 +3,53 @@ ******************************************************************************** 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>`_ + + + -.. image:: ./images/healpix.png - :scale: 50% - :alt: HEALPix |