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| author | Even Rouault <even.rouault@spatialys.com> | 2019-10-03 13:58:19 +0200 |
|---|---|---|
| committer | Even Rouault <even.rouault@spatialys.com> | 2019-10-03 13:58:19 +0200 |
| commit | 5cd917f6c63cc9d55ad9de8c6fdd07709be9ae37 (patch) | |
| tree | 3677bfbd56a1497572778d551d7a0c666c749759 /docs/source | |
| parent | dca893f02ac822f2ccf5f02a4331920eeb42299a (diff) | |
| download | PROJ-5cd917f6c63cc9d55ad9de8c6fdd07709be9ae37.tar.gz PROJ-5cd917f6c63cc9d55ad9de8c6fdd07709be9ae37.zip | |
ob_tran doc: fix/clarify semantics of o_lat_p/o_lon_p
This is a super confusing topic, but from experiments, and in particular with
the example of Fairgrieve projection, o_lat_p and o_lon_p are the coordinates
of the North pole of the unrotated geographic CRS expressed in the rotated
geographic CRS.
This is different from defining a 'new pole', which would be the coordinates
of the rotated North pole expressed in the unrotated CRS.
Diffstat (limited to 'docs/source')
| -rw-r--r-- | docs/source/operations/projections/ob_tran.rst | 11 |
1 files changed, 6 insertions, 5 deletions
diff --git a/docs/source/operations/projections/ob_tran.rst b/docs/source/operations/projections/ob_tran.rst index 378f1333..3a23259d 100644 --- a/docs/source/operations/projections/ob_tran.rst +++ b/docs/source/operations/projections/ob_tran.rst @@ -19,9 +19,10 @@ oblique projection by means of the General Oblique Transformation. The user performs the oblique transformation by selecting the oblique projection ``+proj=ob_tran``, specifying the translation factors, :option:`+o_lat_p`, and :option:`+o_lon_p`, and the projection to be used, :option:`+o_proj`. In the -example of the Fairgrieve projection the latitude and longitude of the pole of -the new coordinates, :math:`\alpha` and :math:`\beta` respectively, are to be placed -at 45°N and 90°W and use the :ref:`moll` projection. Because the central meridian +example of the Fairgrieve projection, the latitude and longitude of the North pole +of the unrotated geographic CRS, :math:`\alpha` and :math:`\beta` respectively, +expressed in the rotated geographic CRS, are to be placed +at 45°N and 90°W and the :ref:`moll` projection is used. Because the central meridian of the translated coordinates will follow the :math:`\beta` meridian it is necessary to translate the translated system so that the Greenwich meridian will pass through the center of the projection by offsetting the central meridian. @@ -50,11 +51,11 @@ New pole .. option:: +o_lat_p=<latitude> - Latitude of new pole for oblique projection. + Latitude of the North pole of the unrotated source CRS, expressed in the rotated geographic CRS. .. option:: +o_lon_p=<longitude> - Longitude of new pole for oblique projection. + Longitude of the North pole of the unrotated source CRS, expressed in the rotated geographic CRS. Rotate about point ................................................................................ |