;
; This example shows how to create a polar stereographic plot with 
; the lat/lon grid labeled.
;
begin

;
; Create an X workstation to draw on.
;
  wid = create "map" xWorkstationClass defaultapp end create

;
; Create a polar stereographic map.
;
  mpid = create "mapplot" mapPlotClass wid
     "vpXF"                  : 0.10    ; Change the location and
     "vpYF"                  : 0.90    ; the width and height
     "vpWidthF"              : 0.78    ; of the map.
     "vpHeightF"             : 0.78

     "mpProjection"          : "Stereographic"
     "mpCenterLatF"          :  90.0           ; Change the center of
     "mpCenterLonF"          : -90.0           ; the projection.

     "mpEllipticalBoundary"  : True    ; Here's what makes it elliptical.

     "mpLimitMode"           : "LatLon"  ; Change the map limit mode
     "mpMinLatF"             :    0.0    ; so that only the northern
     "mpMaxLatF"             :   90.0    ; hemisphere is visible.
     "mpMinLonF"             : -180.0
     "mpMaxLonF"             :  180.0
  end create

;
; Draw the map.
;
  draw(mpid)

;
; Change the viewport of the map object we just created to generate a
; new data space for lat/lon text. Make the new viewport slightly larger
; than the one the map was drawn in, because we want to draw the
; labels on the outside of the map.
;
  setvalues mpid
      "vpXF"      : 0.07
      "vpYF"      : 0.93
      "vpWidthF"  : 0.84
      "vpHeightF" : 0.84
  end setvalues

;
; Create a generic TextItem object that we'll use to label the lat/lon
; grid.  
;
  txid = create "text" textItemClass wid
      "txFont"         : 22     ; Change the font to 22 (helvetica).
      "txFontHeightF"  : 0.015  ; Change the size of the font.
  end create

;
; Define an array of strings to label the longitude values.
;
  labels = (/"0","30E","60E","90E","120E","150E","180","150W",\
             "120W","90W","60W","30W"/)

;
; Create the lat/lon coordinates where you want labels to appear.
; In this case, we want the labels to appear at the equator (lat=0),
; and at longitude values of 0, 30, 60, ..., 330.
;
  lat = fspan(0.,0.,12)
  lon = fspan(0.,330.,12)

;
; Create arrays to hold the NDC values that we're going to convert 
; the lat/lon values to.
;
  xndc = new(dimsizes(lon),float)
  yndc = new(dimsizes(lat),float)

;
; Convert lat/lon coordinates to NDC coordinates since we are 
; drawing the labels in NDC space and NOT in lat/lon space.
;
  datatondc(mpid,lon,lat,xndc,yndc)

;
; Draw each string.
;
  do i=0,dimsizes(labels)-1
    setvalues txid
       "txString" : labels(i)
       "txPosXF"  : xndc(i)
       "txPosYF"  : yndc(i)
    end setvalues

    draw(txid)
  end do

;
; Advance the frame.
;
  frame(wid)
    
end