;REQUIRES: VECT.PRO

;Here's a way to plot a 2-D flow field over a contour
;plot on the globe. This program is configured to use 
;the differences between two fields, but it can be 
;modified to show just one field. Values less than 
;zero appear shaded. 

;It is configured for PS output, but the colors can be 
;easily tweaked for acceptable X output.  

;A call is made to VECT.PRO, a (slight) modification to
;VELVECT.PRO that is found in ../idl_x/bin/

vaa=''
vab=''
vac=''
vad=''
vae=''
vaf=''
read,vaa,promp='Enter U1:  '
read,vab,promp='Enter V1:  '
read,vac,promp='Enter VEL1: '
read,vad,promp='Enter U2: '
read,vae,promp='Enter V2: '
read,vaf,promp='Enter VEL2: '
openr,1,vaa
openr,2,vab
openr,3,vac
openr,4,vad
openr,5,vae
openr,6,vaf
rmf,1,udat1,320,642
rmf,2,vdat1,320,642
rmf,3,veldat1,320,642
rmf,4,udat2,320,642
rmf,5,vdat2,320,642
rmf,6,veldat2,320,642
udata=udat1-udat2
vdata=vdat1-vdat2
veldata=veldat1-veldat2
udata=rotate(udata,3)
vdata=rotate(vdata,3)
veldata=rotate(veldata,3)
udata=shift(udata,341)
vdata=shift(vdata,341)
veldata=shift(veldata,341)
map_set,0,0,title='      '
lats=[-90,-60,-30,0,30,60,90]
latnames=[' ','60 S','30 S',' EQ',' 30 N','60 N',' ']
lons=[-180,-150,-120,-90,-60,-30,0,30,60,90,120,150,180]
lonnames=[' ','150 W','120 W','90 W','60 W','30 W','0','30 E','60 E','90 E','120 E','150 E',' ']
lon=findgen(642)*.5606-180.
lat=findgen(320)*.5625-89.9
udata=congrid(udata,40,20)
vdata=congrid(vdata,40,20)
lonc=congrid(lon,40)
latc=congrid(lat,20)
contour,veldata,lon,lat,/overplot,levels=[min(veldata),0],/fill,c_colors=[190,255]
contour,veldata,lon,lat,/overplot,levels=[-20,-10,0,10,20],/follow,$
c_labels=[1,1,1,1,1,1],c_linesty=[1,1,0,0,0]
vect,udata,vdata,lonc,latc,/overplot
map_grid,label=1,lats=lats,latnames=latnames,latlab=-175.,$
lons=lons,lonnames=lonnames,lonlab=-88.
map_continents,linesty=[0]
free_lun,1,2,3,4,5,6
end