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Projection Specifications
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GMT offers 31 map projections. These are specified using the **-J** common option.
There are two conventions you may use: (a) GMT-style syntax and (b) **Proj4**\ -style syntax.
The projection codes for the GMT-style and the **Proj4**-style are tabulated below.

.. Substitution definitions:
.. |lon0| replace:: lon\ :sub:`0`
.. |lat0| replace:: lat\ :sub:`0`
.. |lon1| replace:: lon\ :sub:`1`
.. |lat1| replace:: lat\ :sub:`1`
.. |lat2| replace:: lat\ :sub:`2`
.. |lonp| replace:: lon\ :sub:`p`
.. |latp| replace:: lat\ :sub:`p`

+----------------------------------------------------------------------------------------+-------------------------------------------------------------------------------------------+-----------------------------------------------------------------+
| GMT PROJECTION CODES                                                                   | Proj4 PROJECTION CODES                                                                    |                                                                 |
+========================================================================================+===========================================================================================+=================================================================+
| **-J** (upper case for *width*, lower case for *scale*)                                | **-J** (lower case for *scale* only)                                                      |                                                                 |
+----------------------------------------------------------------------------------------+-------------------------------------------------------------------------------------------+-----------------------------------------------------------------+
| **-JA**\ |lon0|/|lat0|\ [/\ *horizon*]/\ *width*                                       | **-Jlaea/**\ |lon0|/|lat0|\ [/\ *horizon*]/\ *scale*                                      | Lambert azimuthal equal area :ref:`... <-Ja_full>`              |
+----------------------------------------------------------------------------------------+-------------------------------------------------------------------------------------------+-----------------------------------------------------------------+
| **-JB**\ |lon0|/|lat0|/|lat1|/|lat2|/\ *width*                                         | **-Jaea/**\ |lon0|/|lat0|/|lat1|/|lat2|/\ *scale*                                         | Albers conic equal area :ref:`... <-Jb_full>`                   |
+----------------------------------------------------------------------------------------+-------------------------------------------------------------------------------------------+-----------------------------------------------------------------+
| **-JC**\ |lon0|/|lat0|/\ *width*                                                       | **-Jcass/**\ |lon0|/|lat0|/\ *scale*                                                      | Cassini cylindrical :ref:`... <-Jc_full>`                       |
+----------------------------------------------------------------------------------------+-------------------------------------------------------------------------------------------+-----------------------------------------------------------------+
| **-JCyl_stere/**\ [|lon0|\ [/|lat0|/]]\ *width*                                        | **-Jcyl_stere/**\ [|lon0|\ [/|lat0|]/]\ *scale*                                           | Cylindrical stereographic :ref:`... <-Jcyl_stere_full>`         |
+----------------------------------------------------------------------------------------+-------------------------------------------------------------------------------------------+-----------------------------------------------------------------+
| **-JD**\ |lon0|/|lat0|/|lat1|/|lat2|/\ *width*                                         | **-Jeqdc/**\ |lon0|/|lat0|/|lat1|/|lat2|/\ *scale*                                        | Equidistant conic :ref:`... <-Jd_full>`                         |
+----------------------------------------------------------------------------------------+-------------------------------------------------------------------------------------------+-----------------------------------------------------------------+
| **-JE**\ |lon0|/|lat0|\ [/\ *horizon*]/\ *width*                                       | **-Jaeqd/**\ |lon0|/|lat0|\ [/\ *horizon*]/\ *scale*                                      | Azimuthal equidistant :ref:`... <-Je_full>`                     |
+----------------------------------------------------------------------------------------+-------------------------------------------------------------------------------------------+-----------------------------------------------------------------+
| **-JF**\ |lon0|/|lat0|\ [/\ *horizon*]/\ *width*                                       | **-Jgnom/**\ |lon0|/|lat0|\ [/\ *horizon*]/\ *scale*                                      | Azimuthal gnomonic :ref:`... <-Jf_full>`                        |
+----------------------------------------------------------------------------------------+-------------------------------------------------------------------------------------------+-----------------------------------------------------------------+
| **-JG**\ |lon0|/|lat0|\ [/\ *horizon*]/\ *width*                                       | **-Jortho/**\ |lon0|/|lat0|\ [/\ *horizon*]/\ *scale*                                     | Azimuthal orthographic :ref:`... <-Jg_full>`                    |
+----------------------------------------------------------------------------------------+-------------------------------------------------------------------------------------------+-----------------------------------------------------------------+
| **-JG**\ |lon0|/|lat0|/\ *alt*/*azim*/*tilt*/*twist*/*W*/*H*/*width*                   | **-Jnsper/**\ |lon0|/|lat0|/\ *alt*/*azim*/*tilt*/*twist*/*W*/*H*/*scale*                 | General perspective :ref:`... <-Jg_full>`                       |
+----------------------------------------------------------------------------------------+-------------------------------------------------------------------------------------------+-----------------------------------------------------------------+
| **-JH**\ [|lon0|/]\ *width*                                                            | **-Jhammer/**\ |lon0|/\ *scale*                                                           | Hammer equal area :ref:`... <-Jh_full>`                         |
+----------------------------------------------------------------------------------------+-------------------------------------------------------------------------------------------+-----------------------------------------------------------------+
| **-JI**\ [|lon0|/]\ *width*                                                            | **-Jsinu/**\ |lat0|/\ *scale*                                                             | Sinusoidal equal area :ref:`... <-Ji_full>`                     |
+----------------------------------------------------------------------------------------+-------------------------------------------------------------------------------------------+-----------------------------------------------------------------+
| **-JJ**\ [|lon0|/]\ *width*                                                            | **-Jmill/**\ |lon0|/\ *scale*                                                             | Miller cylindrical :ref:`... <-Jj_full>`                        |
+----------------------------------------------------------------------------------------+-------------------------------------------------------------------------------------------+-----------------------------------------------------------------+
| **-JKf**\ [|lon0|/]\ *width*                                                           | **-Jeck4/**\ |lon0|/\ *scale*                                                             | Eckert IV equal area :ref:`... <-Jk_full>`                      |
+----------------------------------------------------------------------------------------+-------------------------------------------------------------------------------------------+-----------------------------------------------------------------+
| **-JKs**\ [|lon0|/]\ *width*                                                           | **-Jeck6/**\ |lon0|/\ *scale*                                                             | Eckert VI equal area :ref:`... <-Jk_full>`                      |
+----------------------------------------------------------------------------------------+-------------------------------------------------------------------------------------------+-----------------------------------------------------------------+
| **-JL**\ |lon0|/|lat0|/|lat1|/|lat2|/\ *width*                                         | **-Jlcc/**\ |lon0|/|lat0|/|lat1|/|lat2|/\ *scale*                                         | Lambert conic conformal :ref:`... <-Jl_full>`                   |
+----------------------------------------------------------------------------------------+-------------------------------------------------------------------------------------------+-----------------------------------------------------------------+
| **-JM**\ [|lon0|\ [/|lat0|]/]\ *width*                                                 | **-Jmerc/**\ [|lon0|\ [/|lat0|/]]\ *scale*                                                | Mercator cylindrical :ref:`... <-Jm_full>`                      |
+----------------------------------------------------------------------------------------+-------------------------------------------------------------------------------------------+-----------------------------------------------------------------+
| **-JN**\ [|lon0|/]\ *width*                                                            | **-Jrobin/**\ [|lon0|/]\ *scale*                                                          | Robinson :ref:`... <-Jn_full>`                                  |
+----------------------------------------------------------------------------------------+-------------------------------------------------------------------------------------------+-----------------------------------------------------------------+
| **-JOa**\ |lon0|/|lat0|/\ *azim*/*width*                                               | **-Jomerc/**\ |lon0|/|lat0|/\ *azim*/*scale*                                              | Oblique Mercator, 1: origin and azim   :ref:`... <-Jo_full>`    |
+----------------------------------------------------------------------------------------+-------------------------------------------------------------------------------------------+-----------------------------------------------------------------+
| **-JOb**\ |lon0|/|lat0|/|lon1|/|lat1|/\ *width*                                        | **-Jomerc/**\ |lon0|/|lat0|/|lon1|/|lat1|/\ *scale*                                       | Oblique Mercator, 2: two points :ref:`... <-Jo_full>`           |
+----------------------------------------------------------------------------------------+-------------------------------------------------------------------------------------------+-----------------------------------------------------------------+
| **-JOc**\ |lon0|/|lat0|/|lonp|/|latp|/\ *width*                                        | **-Jomercp/**\ |lon0|/|lat0|/|lonp|/|latp|/\ *scale*                                      | Oblique Mercator, 3: origin and pole :ref:`... <-Jo_full>`      |
+----------------------------------------------------------------------------------------+-------------------------------------------------------------------------------------------+-----------------------------------------------------------------+
| **-JP**\ [**a**]\ *width*\ [/*origin*][\ **r**\ \|\ **z**]                             | **-Jpolar/**\ [**a**]\ *scale*\ [/*origin*][**r**\ \|\ **z**]                             | Polar [azimuthal] (:math:`\theta, r`) (or cylindrical)          |
+----------------------------------------------------------------------------------------+-------------------------------------------------------------------------------------------+-----------------------------------------------------------------+
| **-JPoly**\ [|lon0|\ [/|lat0|]/]\ *width*                                              | **-Jpoly/**\ [|lon0|\ [/|lat0|/]]\ *scale*                                                | (American) polyconic :ref:`... <-Jpoly_full>`                   |
+----------------------------------------------------------------------------------------+-------------------------------------------------------------------------------------------+-----------------------------------------------------------------+
| **-JQ**\ [|lon0|\ [/|lat0|/]]\ *width*                                                 | **-Jeqc/**\ [|lon0|\ [/|lat0|/]]\ *scale*                                                 | Equidistant cylindrical :ref:`... <-Jq_full>`                   |
+----------------------------------------------------------------------------------------+-------------------------------------------------------------------------------------------+-----------------------------------------------------------------+
| **-JR**\ [|lon0|/]\ *width*                                                            | **-Jwintri/**\ [|lon0|/]\ *scale*                                                         | Winkel Tripel :ref:`... <-Jr_full>`                             |
+----------------------------------------------------------------------------------------+-------------------------------------------------------------------------------------------+-----------------------------------------------------------------+
| **-JS**\ |lon0|/|lat0|\ [/\ *horizon*]/\ *width*                                       | **-Jstere/**\ |lon0|/|lat0|\ [/\ *horizon*]/\ *scale*                                     | General stereographic :ref:`... <-Js_full>`                     |
+----------------------------------------------------------------------------------------+-------------------------------------------------------------------------------------------+-----------------------------------------------------------------+
| **-JT**\ [|lon0|\ [/|lat0|]/]\ *width*                                                 | **-Jtmerc/**\ [|lon0|\ [/|lat0|/]]\ *scale*                                               | Transverse Mercator :ref:`... <-Jt_full>`                       |
+----------------------------------------------------------------------------------------+-------------------------------------------------------------------------------------------+-----------------------------------------------------------------+
| **-JU**\ *zone*/*width*                                                                | **-Jutm/**\ *zone*/*scale*                                                                | Universal Transverse Mercator (UTM) :ref:`... <-Ju_full>`       |
+----------------------------------------------------------------------------------------+-------------------------------------------------------------------------------------------+-----------------------------------------------------------------+
| **-JV**\ [|lon0|/]\ *width*                                                            | **-Jvandg/**\ [|lon0|/]\ *scale*                                                          | Van der Grinten :ref:`... <-Jv_full>`                           |
+----------------------------------------------------------------------------------------+-------------------------------------------------------------------------------------------+-----------------------------------------------------------------+
| **-JW**\ [|lon0|/]\ *width*                                                            | **-Jmoll/**\ [|lon0|/]\ *scale*                                                           | Mollweide :ref:`... <-Jw_full>`                                 |
+----------------------------------------------------------------------------------------+-------------------------------------------------------------------------------------------+-----------------------------------------------------------------+
| **-JX**\ *width*\ [**l**\ \|\ **p**\ *exp*\ \|\                                        | **-Jxy**\ *xscale*\ [**l**\ \|\ **p**\ *exp*\ \|\                                         | Linear, log\ :math:`_{10}`, :math:`x^a-y^b`, and time           |
| **T**\ \|\ **t**][/\ *height*\ [**l**\ \|\ **p**\                                      | **T**\ \|\ **t**][/\ *yscale*\ [**l**\ \|\ **p**\                                         | :ref:`... <-Jx_full>`                                           |
| *exp*\ \|\ **T**\ \|\ **t**]][**d**]                                                   | *exp*\ \|\ **T**\ \|\ **t**]][**d**]                                                      |                                                                 |
+----------------------------------------------------------------------------------------+-------------------------------------------------------------------------------------------+-----------------------------------------------------------------+
| **-JY**\ |lon0|/|lat0|/\ *width*                                                       | **-Jcea/**\ |lon0|/|lat0|/\ *scale*                                                       | Cylindrical equal area :ref:`... <-Jy_full>`                    |
+----------------------------------------------------------------------------------------+-------------------------------------------------------------------------------------------+-----------------------------------------------------------------+
