Dear Heiko
Thanks for raising this. I suppose it might depend on whether you are thinking
of transforming into the map projection, or out of it. But in any case, if it
is unclear or wrong, it should be corrected. To do that, the procedure is to
open a CF defect trac ticket. The rule for defect tickets (fixing mistakes, not
changing the intention) is that they are accepted by default if no-one objects
in the required time.
Best wishes
Jonathan
----- Forwarded message from Heiko Klein <Heiko.Klein at met.no> -----
> Date: Mon, 9 Mar 2015 14:12:17 +0100
> From: Heiko Klein <Heiko.Klein at met.no>
> To: "cf-metadata at cgd.ucar.edu" <cf-metadata at cgd.ucar.edu>
> Subject: [CF-metadata] Wrong definition for false-easting/false-northing?
> User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101
> Thunderbird/31.5.0
>
> Hi,
>
> the cf-convention in Table F.1 Grid Mapping Attributes explains
> false-easting/northing as:
>
> The value added to all abscissa values in the rectangular
> coordinates for a map projection.
>
>
>
> I think it must be 'The value subtracted from all abscissa values...':
>
> false_easting = 0 ... proj_x_axis_value(0) = -200000
> is equivalent to
> false_easting = 200000 ... proj_x_axis value(0) = 0
>
>
> or in proj.4-term (+x_0 = false_easting):
> $ proj -I +proj=stere +R=6370000
> -200000 -200000
> 1d47'57.196"W 1d47'54.005"S
>
> heikok at pc4027:~$ proj -I +proj=stere +R=6370000 +x_0=200000 +y_0=200000
> 0 0
> 1d47'57.196"W 1d47'54.005"S
>
>
>
> I tested it with the netcdf-java and other programs, too.
> False_easting/northing values are subtracted from the x-Axis values.
>
> Best regards,
>
> Heiko
>
>
>
> --
> Dr. Heiko Klein Tel. + 47 22 96 32 58
> Development Section / IT Department Fax. + 47 22 69 63 55
> Norwegian Meteorological Institute http://www.met.no
> P.O. Box 43 Blindern 0313 Oslo NORWAY
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----- End forwarded message -----
Received on Mon Mar 09 2015 - 10:27:58 GMT
