Hi Phil,
Not entirely sure what you're after (a picture may have helped), but I
know Basemap has relatively recently added rotated pole coordinate
system support which may be of use. I'm not sure how well that goes
with the meridian/parallel drawing within Basemap though.
Indeed, a picture is always better! And in fact I forgot to mention how
the prime meridian is defined.
http://wdc.kugi.kyoto-u.ac.jp/igrf/gggm/gmexp.html
In summary:
1. The north pole in the geomagnetic coordinate system is the
geomagnetic north pole (and the same with the south pole).
2. The prime meridian passes through the geographic and geomagnetic poles.
I think basemap's rotated pole system is not applicable here. If I
understood correctly then the data is just represented in rotated pole
coordinates (I guess to avoid having data that goes through the
discontinuity or the poles) but for the actual drawing they are
transformed back to geographic coordinates and everything happens like
usual.
Alternatively, if I've understood you correctly, I've put together an
example using cartopy which first produces a map in "Geomagnetic"
space (with traditional latitude and longitude meridians/parallels)
and then by drawing a north polar stereographic map first with the
geomagnetic latitudes and longitudes (for 2010) next to the WGS84
latitudes and longitudes.
Notebook can be found
http://nbviewer.ipython.org/gist/pelson/7b461a798e454533d4ef
The key is that you can make a map of any projection, and later add
data from any source coordinate system (transform) and they should
play nicely in Cartopy.
I think this should work and I like the way this is done in Cartopy
(haven't used it yet). How would I define the prime meridian here?
Cheers
Maik
Is this the kind of thing you're after?
Cheers,
Phil
On 12 May 2014 13:18, Maik Riechert <maik.riech...@arcor.de
<mailto:maik.riech...@arcor.de>> wrote:
Hi,
I'm drawing a stereographic map, my data is in geographic latitude,
longitude coordinates. But instead of drawing parallels/meridians
based
on the geographic poles I need to draw them based on the geomagnetic
poles, that is, the poles are rotated. E.g. in 2010 the north
geomagnetic pole was at 80.08°N 72.21°W
(https://en.wikipedia.org/wiki/Geomagnetic_pole). In my case it's for
aurora research, and many existing maps are drawn in this way, so
naturally it becomes easier to compare them if they are based on the
same coordinate system.
Is this somehow achievable with basemap? Note that I'd like to draw
country borders etc. as well. (Otherwise I could just transform my
geographic coordinates to magnetic coordinates and use standard
basemap.)
Thanks
Maik
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