Andrew Straw wrote: > I've been playing around with stereographic projections, and it appears > that the bounding-box for the 'stere' projection isn't computed. Being > blissfully unaware of all the complexities involved, I thought I'd send > this email to see if there's an easy way to deal with the situation. > > Basically, I'm trying to plot on an equatorial stereographic projection > created like so: > > m=Basemap(projection='stere', lat_ts = 0.0, lat_0 = 0, lon_0 = 90.0) > > This creates a projection that seems to work well, but the problem is > that the [ll|ur]crn* attributes aren't set to anything useful, meaning > that lots of the nice basemap goodies aren't working (drawmeridians, etc.) > Andrew: The [ll|ur]crn* have default values which don't work very well for the stereographic projection (-90,+90,-180,+180). You'll have to set them yourself when you create the Basemap instance. > (Note: I don't really understand what the lat_ts is doing -- the > docstring says it is the "natural origin". I can't find reference to > this at http://en.wikipedia.org/wiki/Stereographic_projection . I guess > this is related to the discussion of "scale error at the extremities" > at > http://www.remotesensing.org/geotiff/proj_list/oblique_stereographic.html > , and thus I assume that if lat_ts is set to lat_0, the scale factor > will be 1 at the point of tangency. ) > AFAICT, lat_ts is the latitude of 'true scale', whatever that means. I set the docstring based upon the info at http://www.remotesensing.org/geotiff/proj_list/polar_stereographic.html. > So, the question is, can some default bounding box be computed for > equatorial (and possibly oblique) stereographic projections in any > reasonable way? It would be nice to make plots like those found on the > wikipedia page. >
You should be able to make all those plots without too much difficulty - just some trial and error in choosing the corners of the plot region. If you are making a polar stereographic projection, you can use projection='npstere' or 'spstere' and set the bounding latitude (the latitude that is tangent to the plot boundary - see the polarmaps.py example) and Basemap will determine the corners for you automatically. I don't know of any obvious way to do this for the equatorial case - it's pretty hard to guess what the user might want. I welcome any suggestions though. -Jeff -- Jeffrey S. Whitaker Phone : (303)497-6313 NOAA/OAR/CDC R/PSD1 FAX : (303)497-6449 325 Broadway Boulder, CO, USA 80305-3328 ------------------------------------------------------------------------- Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642 _______________________________________________ Matplotlib-users mailing list Matplotlib-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/matplotlib-users
