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[CF-metadata] need reference for rotated pole grid mapping

From: Heiko Klein <Heiko.Klein>
Date: Fri, 20 Apr 2012 15:19:46 +0200

Hi John,

I'm not completely sure if this is what you want, but I can provide an
example:
http://thredds.met.no/thredds/catalog/metno/proff4km/default/catalog.html

grid_mapping_name: rotated_latitude_longitude
grid_north_pole_longitude: 156.0
grid_north_pole_latitude: 23.5


This refers to an oblique transformation of the latitude longitude
values. The corresponding proj.4 string is:

+proj=ob_tran +o_proj=longlat +lon_0=-24 +o_lat_p=23.5


Conversion between CF and proj.4 is:

grid_north_pole_longitude = normalize180(180 + lon_0)
grid_north_pole_latitude = o_lat_p

where normalize180 makes sure that grid_north_pole_longitude stays
within [-180,180].



We are using private EPSG-codes (e.g. we haven't uploaded them to
http://spatialreference.org), so nothing to use as reference here. And I
have no example with north_pole_grid_longitude, and I don't know if it
is +o_lon_b or similar?

As a reference, I used http://download.osgeo.org/proj/proj.4.3.I2.pdf
chapter 4: Creating oblique projections

Best regards,

Heiko



On 2012-04-19 18:49, John Caron wrote:
> This grid mapping has no reference implementation or any other
> documentation. I think we have to have something. Can anyone supply?
>
>
> 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:/
>
>
Received on Fri Apr 20 2012 - 07:19:46 BST

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