Re: RotatedMercator map projection

Ah! I get it now. I didn't realize they were different. Thank you!

So, it turns out my data is actually rotated pole. I have lat2d & lon2d arrays, so the data is showing up in the right place on the map, but I want to use a map projection that will make it square. Any thoughts? In Ezmap terms, I believe it has non-zero PLAT & PLON. Is that what mpCenterLatF & mpCenterLonF specify for the normal Mercator projection?

--Seth

>Hi Seth,
>The RotatedMercator projection is not actually the same as a rotated pole projection. It ignores the 'mpCenterLatF' value,
>and the 'mpCenterRotF' value behaves in a different manner from the normal Mercator projection.
>You will see the difference if you give 'mpCenterRotF' a non-zero value.
>
>For an explanation of the difference between these projections from the perspective of the underlying software, see:
>
>http://www.ncarg.ucar.edu/supplements/ezmap/#PROJECTIONS
>
>Scroll down to 'Cylindrical Projections'
>
>If the grid is plotted in its native projection then you must either have the tfDoNDCOverlay flag set True, or you are not communicating
>the 2d coordinates correctly to the plotting routine.
>
> -dave
>
>
>
>On Sep 15, 2008, at 4:17 PM, Seth McGinnis wrote:
>
>> Does anyone have any examples of how to plot data that's in a
>> rotated Mercator (aka rotated pole or rotated lat-lon) coordinate
>> system?
>>
>> I've been making plots using the following map projection resources:
>>
>> res_at_mpProjection = "RotatedMercator"
>> res_at_mpCenterLonF = 83
>> res_at_mpCenterLatF = 42.5
>>
>> and as far as I can tell, it doesn't look any different than
>> leaving the projection unspecified. (The data has lat2d and lon2d
>> arrays. Using the same attributes with the corresponding values
>> for data in a polar stereographic or transverse mercator projection
>> results in the native grid being plotted square on the page.)
>> Maybe I have the wrong values there, but I tried it with
>> mpCenterLatF = 0, 45, and 90, and it made no difference to the
>> resulting plot. Should I be specifying the projection parameters
>> in a different way?
>>
>> The only examples I can find of the RotatedMercator projection on
>> the NCL website are in the "Map Only" application examples 12 & 13,
>> and it looks to me like the RotatedMercator example is identical to
>> the Mercator example.
>>
>> Thanks,
>>
>> --Seth
>>
>> ----
>> Seth McGinnis
>> Associate Scientist
>> ISSE / NCAR
>> ----
>> _______________________________________________
>> ncl-talk mailing list
>> ncl-talk_at_ucar.edu
>> http://mailman.ucar.edu/mailman/listinfo/ncl-talk
>

_______________________________________________
ncl-talk mailing list
ncl-talk_at_ucar.edu
http://mailman.ucar.edu/mailman/listinfo/ncl-talk
Received on Tue Sep 16 2008 - 00:56:40 MDT