Messages from Usenet group comp.lang.idl-pvwave, compiled by Paulo Penteado
Hi, supposedly, someone has already run into this problem, and possibly it had already been discussed here, but I'd still like to post the following question: I want to display a global data on a map with the date line in the center, using Mollweide's projection, and continental boundaries. So I do: map_set, /moll, /cont, /hor, 0, 180 The result is a little unsatisfactory, since IDL (at least my Mac Version 4.0.1 does) connects lines accross the Greenwich meridian right through my display. The best solution I could find: map_set, /moll, /cont, /hor, 0, 180, limit = [-90, 0.5, 90, 359.5] I do not find this very elegant, because I might miss out some data points. Doing map_set, /moll, /cont, /hor, 0, 180, limit = [-90, 0.1, 90, 359.9] then has some problems similar to the first version. My question: Does anyone know how to get around this problem? Thanks a lot. Wolfgang Knorr Max-Planck-Institut fuer Meteorologie, Hamburg, GERMANY
Wolfgang Knorr wrote: > > Hi, > > supposedly, someone has already run into this problem, and possibly > it had already been discussed here, but I'd still like to post the > following question: > > I want to display a global data on a map with the date line > in the center, using Mollweide's projection, and continental > boundaries. So I do: > > map_set, /moll, /cont, /hor, 0, 180 > > The result is a little unsatisfactory, since IDL (at least my > Mac Version 4.0.1 does) connects lines accross the Greenwich > meridian right through my display. The best solution I could find: > > map_set, /moll, /cont, /hor, 0, 180, limit = [-90, 0.5, 90, 359.5] > > I do not find this very elegant, because I might miss out some data > points. Doing > > map_set, /moll, /cont, /hor, 0, 180, limit = [-90, 0.1, 90, 359.9] > > then has some problems similar to the first version. > My question: Does anyone know how to get around this problem? > Don't get me started on map_set. I rely on it and spend a great deal of my time creating "work arounds." I don't use /cont when calling map_set, I use a home grown procedure which contours the percentage of a grid box which is land. The resolution is .25 degrees by .25 degrees, and works for the mollweide projection. I can make the source code and data set available to you if you wish. And don't forget the /isotropic keyword! You can specify a particular projection, but you won't get a true projection of that type unless you specify /isotropic! Figure that one out for me. BTW: How does this look? map_set, 0, 180, /cyl, limit=[-30,90,30,300], /cont, /iso map_continents, /fill Ok, I'll stop there. > Thanks a lot. > > Wolfgang Knorr > Max-Planck-Institut fuer Meteorologie, Hamburg, GERMANY -- Andrew F. Loughe afl@cdc.noaa.gov University of Colorado, CIRES http://cdc.noaa.gov/~afl Campus Box 449 phn:(303)492-0707 fax:(303)497-7013 Boulder, CO 80309-0449 "He who laughs last thinks slowest!"