# [Proj] proj4 specifications for a rotated latlon grid on a sphere?

Mikael Rittri Mikael.Rittri at carmenta.com
Tue Aug 14 03:51:40 EST 2012

```That's interesting, Hermann, I didn't know about ob_tran.

After some googling, I found an older post, also by you, where
you also used the flag

-m 57.2957795130823

See

http://lists.maptools.org/pipermail/proj/2011-October/005906.html

and

http://lists.maptools.org/pipermail/proj/2011-October/005913.html

and also

http://lists.maptools.org/pipermail/proj/2010-June/005234.html

On the related topic, here is a reference saying that meteorological
long/lat data on a sphere needs no datum shift to WGS84:

http://www.ie.unc.edu/cempd/projects/mims/spatial/grids_ellipsoids_map_proj.html

Regards,

Mikael Rittri
Carmenta
Sweden
http://www.carmenta.com

-----Original Message-----
From: proj-bounces at lists.maptools.org [mailto:proj-bounces at lists.maptools.org] On Behalf Of Hermann Peifer
Sent: Tuesday, August 14, 2012 1:50 AM
To: PROJ.4 and general Projections Discussions
Subject: Re: [Proj] proj4 specifications for a rotated latlon grid on a sphere?

On 2012-08-13 12:19, Martin Ivanov wrote:
> Dear PROJ4 users,
>
> I have a rotated latitude-longitude grid with coordinates of the north
> pole POLE_LAT=39.25 and POLE_LON=-162.
> The data are on a sphere with radius 6371 km. Is it possible to define
> proj4 specifications for this grid...

You could try:
+proj=ob_tran +o_proj=latlon +o_lon_p=-162 +o_lat_p=39.25 +lon_0=180

Hermann
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