Storm or Ship Tracks

Dear NCL Users:
 
I am using the sample application for trajectories (traj1-traj3.ncl). This shows how to plot trajectories.
 
What I was looking for was the same type of script but rather than just a line showing where a storm
center is going or a ship track is going. I wanted an arrow to mark the last point and the direction of
movement:
 
------x--------x-------> showing the track moving "east"
 
Probably could make a vector out of the last point in do it that way.
 
 
Does anyone know how to plot arrows at the end of a trajectory (included is the sample script that
I used in my application)?.
 
Mahalo,
Craig Motell
Joint Typhoon Warning Center
Honolulu
;*************************************************
; traj_2.ncl
;*************************************************
load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_code.ncl"
load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_csm.ncl"
load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/contributed.ncl"
;**************************************************
begin
;*************************************
; read in data
;************************************
; note this trajectory file contains data in the form of
; 9 variables x 131 timesteps x 100 trajectories
   ntime = 131
   path= "/fs/cgd/home0/murphys/Tutorials/Csm_graphics/special_topics/traj/"

   big = fbinrecread(path+"traj.bin",0,(/9,ntime,100/),"float")
   time= fbinrecread(path+"traj.bin",1,(/ntime/),"float")
;********************************************
   wks = gsn_open_wks("ps","traj") ; open workstation
;*********************************************
; color preps
;*********************************************
  cnLevels=fspan(34.5,34.8,8)
  cmap = RGBtoCmap ("/cgd/cas/murphys/Data/colormaps/redyellowblue.rgb")
  gsn_define_colormap (wks,cmap)

   res = True ; map resources
   res_at_gsnDraw = False ; don't draw
   res_at_gsnFrame = False ; don't advance frame
   res_at_vpWidthF = 0.80 ; make map bigger
   res_at_vpHeightF = 0.80
   res_at_mpMaxLatF = -20 ; select subregion
   res_at_mpMinLatF = -60
   res_at_mpMinLonF = -75
   res_at_mpMaxLonF = -25

; label bar resources
   res_lb = True
   res_lb_at_vpWidthF = 0.60
   res_lb_at_vpHeightF = 0.10
   res_lb_at_lbPerimOn = False ; Turn off perimeter.
   res_lb_at_lbOrientation = "Horizontal" ; Default is vertical.
   res_lb_at_lbLabelStride = 2
   res_lb_at_lbLabelAlignment = "InteriorEdges" ; Default is "BoxCenters".
   res_lb_at_lbFillColors = cmap(2:,:) ; Colors for boxes.
   res_lb_at_lbMonoFillPattern = True ; Fill them all solid.
   res_lb_at_lbLabelFontHeightF = 0.015

   res_at_tiMainString = "Trajectories colored by salinity (ppt)" ; title
  
   map = gsn_csm_map_ce(wks,res) ; create map
;*********************************************
; trajectory parameters
;*********************************************
   xpt = new(ntime,float) ; allocate memory
   ypt = new(ntime,float)
   traj = (/1,10,53,67,80/) ; choose which trajectories to plot

;*********************************************
; some plot parameters
;*********************************************
   pres = True ; polyline resources
   pres_at_gsLineThicknessF = 2.0 ; line thickness

   mres = True ; marker resources
   first = True ; start of traj resources
;********************************
   do i = 0,dimsizes(traj)-1 ; loop through chosen traj
      ypt = big(2,:,traj(i)) ; extract lat from whole array
      xpt = big(1,:,traj(i)) ; extract lon from whole array
      sst = big(8,:,traj(i))

     do j=0,dimsizes(ypt)-2
        pres_at_gsLineColor=GetFillColor(cnLevels,cmap,avg( (/sst(j),sst(j+1)/)))
        gsn_polyline(wks,map,(/xpt(j),xpt(j+1)/),(/ypt(j),ypt(j+1)/),pres)
     end do

; create a unique marker to indicate the start of the trajectory

      first_at_gsMarkerSizeF = 9.0 ; marker size
      first_at_gsMarkerColor = "red" ; marker color

      gsn_polymarker(wks,map,xpt(0),ypt(0),first) ; draw start of traj
      delete(first_at_gsMarkerColor)
      delete(first_at_gsMarkerSizeF)
   end do
   gsn_labelbar_ndc(wks,dimsizes(cnLevels)+1,cnLevels,0.30,0.30,res_lb)
   draw(map)
   frame(wks)
  
end

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Received on Mon Apr 23 2007 - 12:55:52 MDT