Re: plot, lons, lats overlayed on a map

[Liam Gumley <Liam.Gumley(at)ssec.wisc.edu>]

T Bowers wrote:
> How do I create a plot that overlays a map correctly?

The strategy outline in your email will give misleading results even if
you line up the map and plot edges. The orthographic projection does not
give a uniform x/y grid (which you get from PLOT). Thus you need to
create the map projection first, and then plot your points on the map
projection. For example (assuming you have IDL 5.1 or 5.2):

map_set, 35, 125, /ortho, xmargin=[5,5], ymargin=[5,5], scale=10e6
map_grid, /box
map_continents, /hires
oplot, lons, lats, psym=6

You can modify the SCALE keyword to MAP_SET to zoom in or out. It's much
more convenient than using the awkward LIMIT keyword. And the BOX
keyword to MAP_GRID creates lat/lon labels along the map edges.

Cheers,
Liam.

---
Liam E. Gumley
Space Science and Engineering Center, UW-Madison
1225 W. Dayton St., Madison WI 53706, USA
Phone (608) 265-5358, Fax (608) 262-5974
http://cimss.ssec.wisc.edu/~gumley