Hi Maarten,
I cannot access the link you sent. See error message below.
Apart from this: "Rotated Pole" is something special, since it is no
projection, but a transformation. You may try to mimic this transformation by
an appropriate projection (I do not know one and I am not familiar with WMS,
but would be interested, if someone could suggest one).
The definition of the pole seems to be ok. 47./-165. indicates normally an area
over Europe (is this what you expect?), since this means that the rotated grid
is produced by shifting the geographical grid 15 degrees eastward and 43
degrees northward. It depends also on the rlon and rlat values of cause.
Burkhardt
Error {
code = 400;
message = "Unrecognized request";
};
Am 25.04.2012 um 10:39 schrieb Plieger, Maarten (KNMI):
> Hi,
>
> We have a dataset with rotated pole in which the projection definition has an
> unexpected 180 degrees shift if you compare it to the proj definition.
>
> Our WMS derives proj strings for projection from CF projection metadata. In
> order to visualise CF rotated pole I had to shift grid_north_pole_longitude
> by 180 degrees, see the following mapping:
>
> float rotated_pole ;
> rotated_pole:grid_mapping_name = "rotated_latitude_longitude" ;
> rotated_pole:units = "degrees" ;
> rotated_pole:grid_north_pole_latitude = 47.000000f ;
> rotated_pole:grid_north_pole_longitude = -165.000000f ;
>
> equals to:
>
> "+proj=ob_tran +o_proj=longlat +lon_0=15 +o_lat_p=47 +o_lon_p=0 +a=6378.140
> +b=6356.750 +x_0=0 +y_0=0 +no_defs"
>
> Here is a DAP URL if you would like have another example dataset:
> http://opendap.nmdc.eu/knmi/thredds/dodsC/RACMO/experiments/RLOTOS50/ndlotos-cy33r1_nmdc-opendap/3Hourly_data/tsurf.KNMI-2011.RLOTOS50.ndlotos-cy33r1_nmdc-opendap.nc
>
> Is this 180 degree shift not supposed to be needed?
>
> Cheers,
> Maarten
>
>
> -----Oorspronkelijk bericht-----
> Van: [email protected] namens Burkhardt Rockel
> Verzonden: di 24-4-2012 21:11
> Aan: [email protected]
> CC: [email protected]
> Onderwerp: Re: [CF-metadata] rotated pole projection
>
> Hi Don,
>
> this is not a problem in the grid definition, but a problem of the code. This
> is not just a problem in your Java code, but also in the Fortran code that is
> used in regional climate models (and the output files in the link you
> provided are from the Danish regional climate model). It may well be that the
> Java version was derived from the Fortran version.
> This strange thing happens, when the geographic pole and the rotated pole are
> the same or the rotation is just along the equator. In your case you may
> either set grid_north_pole_longitude=180. before entering your Java routine
> or just ignore the rotated pole at all since in this special case it is rlon
> = geographical longitude and rlat = geographical latitude.
>
> Regards
> Burkhardt
>
> Am 24.04.2012 um 18:50 schrieb Don Murray:
>
>> Hi-
>>
>> I have some climate files that have a rotated-pole projection defined as:
>>
>> char rotated_pole ;
>> rotated_pole:grid_mapping_name = "rotated_latitude_longitude" ;
>> rotated_pole:grid_north_pole_latitude = 90.f ;
>> rotated_pole:grid_north_pole_longitude = 0.f ;
>>
>> When I read this through the netCDF-Java library, the data end up 180
>> degrees off from where it is supposed to be (African data is over Hawaii).
>> I talked to John Caron at Unidata and he doesn't know if it is a problem
>> with the grid definition or the rotated-pole code in netCDF-Java.
>>
>> Does anyone on this list have a pointer to the equations for the rotated
>> pole and or know if there anything wrong with the grid mapping definition?
>> Should the above imply a unity transformation?
>>
>> Sample files are at:
>>
>> http://dods-testbed.ictp.it/aap/ENSEMBLES_AMMA/ERAIN/Daily/
>>
>> thanks for the help!
>>
>> Don
>> --
>> Don Murray
>> NOAA/ESRL/PSD and CIRES
>> 303-497-3596
>> http://www.esrl.noaa.gov/psd/people/don.murray/
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>> CF-metadata mailing list
>> [email protected]
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