From: Sebastian Krieger <sebastian@io...>  20080531 02:27:42

Dear all! I would like to ask two questions: one concerning imshow with the Robinson projection and the second about the latitude limits for the same map projection. First, I am trying to make a Robinson projection map using imshow instead of contourf as described in the Basemap documentation. I modified the script as follows: # from matplotlib.toolkits.basemap import Basemap, shiftgrid from pylab import load, meshgrid, title, arange, show, cm, pi # # read in topo data (on a regular lat/lon grid) etopo = load('etopo20data.gz') lons = load('etopo20lons.gz') lats = load('etopo20lats.gz') # # create Basemap instance for Robinson projection. m = Basemap(projection='robin',lon_0=0.5*(lons[0]+lons[1])) # # compute native map projection coordinates for lat/lon grid. etopo, lons = shiftgrid(180., etopo, lons, start=False) x, y = m(*meshgrid(lons,lats)) dx = 2.*pi*m.rmajor/len(lons) nx = int((m.xmaxm.xmin)/dx)+1; ny = int((m.ymaxm.ymin)/dx)+1 dat, x, y = m.transform_scalar(etopo, lons, lats, nx, ny, returnxy=True) # # make filled contour plot. im = m.imshow(dat, cmap=cm.jet) m.drawcoastlines() # draw coastlines m.drawmapboundary() # draw a line around the map region m.drawparallels(arange(90.,120.,30.),labels=[1,0,0,0]) # draw parallels m.drawmeridians(arange(0.,420.,60.),labels=[0,0,0,1]) # draw meridians title('Robinson Projection') # add a title show() # The result looks as I would expect, except that some data is plot outside of the map boundaries. Using another projection as the Orthographic for example, this problem doesn't happen. Am I doing something wrong? Second, I work with Topex/POSEIDON and Jason1 sea surface height anomalies datasets where the latitudes range from about 67.5S to 67.5N. Outside these limits hopefully its blank, as anyone would expect. Aesthetically I find it more appealing if I could limit my map boundaries to these limits, or even lower limits if I zoom the equatorial region. Has anyone ever tried to do this? Thank's in advance and kind regards, Sebastian 