Hi John,
Rotated pole grid mapping is not a projection but a transformation. This
is why it cannot be found in documents describing projections. Maybe it
can be found in books about mathematics or physics, when it comes to
transformation of spherical coordinate systems.
Rotated coordinates are often used in regional forecast and climate models
as internal model coordinate.
In the rotated coordinate system the pole is tilt and can be positioned
such that the equator runs through the centre of the model domain. Thus
problems resulting from the convergence of the meridians can be minimized
for any limited area model domain on the globe.
> * grid_north_pole_latitude
> * grid_north_pole_longitude
are the latitude and longitude of the north pole in rotated system with
respect to the "real" geographical system.
> * north_pole_grid_longitude - This parameter is option (default
is 0).
after tilting the pole to another place on the globe you may also rotated
the new system along the pole axis. However, this is rarely done.
Please find enclosed an example file.
Regards
Burkhardt
cf-metadata-bounces at cgd.ucar.edu wrote on 01.08.2007 17:10:29:
> The docs on Rotated pole grid mapping could probably use some
> clarification heres whats there:
>
> ------------------
>
> Example F.6. Rotated pole
>
> grid_mapping_name = rotated_latitude_longitude
> Map parameters:
>
> * grid_north_pole_latitude
> * grid_north_pole_longitude
> * north_pole_grid_longitude - This parameter is option (default
is 0).
>
> Map coordinates:
>
> The rotated latitude and longitude coordinates are identified by
> the standard_name attribute values grid_latitude and grid_longitude
> respectively.
>
> Notes:
>
> ---------------
>
> Theres no explanation of the parameters, nor a reference. The 3rd
> (north_pole_grid_longitude) is particularly obscure. I also see a
> type in section 5.6. Can anyone point me to a reference describing
> this projection?
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Received on Wed Aug 01 2007 - 13:39:15 BST
