pro deprob_demo


  ; planet geometry
  a = 71492.0  /0.7     
  b = 66854.0  

  lat_se = 31. 
  lon_se = 274.


  ; setup the x-y grid image
  xdim = 512
  ydim = 512

  ctr_xpix = 250
  ctr_ypix = 250

  pix2km = 500

  x = (dindgen(xdim) - ctr_xpix) * pix2km
  y = (dindgen(xdim) - ctr_ypix) * pix2km

  xsq = dblarr(xdim, ydim)
  ysq = dblarr(xdim, ydim)
  for i = 0,xdim-1 do begin
      xsq[*,i] = x
      ysq[i,*] = y
  endfor

  
  ; now xsq is a 512x512 image where the values are the horizontal
  ; distance from the "center" in km, and ysq is a 512x512 image 
  ; where the values are the vertical distance from the center.

  ob = deprob(xsq, ysq, a, b, lat_se, lon_se, npang=17.)



  imlon = (ob.lon > 0) mod 10
  imlat = abs(ob.lat) mod 10
  space = where(ob.lat eq -666, nspace)

  loadct, 32
  tvscl, imlon

  imgrid = fltarr(xdim, ydim)
  if nspace gt 0 then imlat(space) = 666
  if nspace gt 0 then imlon(space) = 666
  imgrid(where(imlat lt 0.5)) = 100
  imgrid(where(imlon lt 0.5)) = 95
  if nspace gt 0 then imlat(space) = -666

  tvscl, imgrid +imlat >0, 512,0



end