plot_traveltime_sr
 
  Call 
     plot_traveltime(S,R)
     S: [n,2] : source locattion
     R: [n,2] : reveiver locattion
     or (3d)
     S: [n,3] : source locattion
     R: [n,3] : reveiver locattion
 
 
  EX:
   % 2D
   D=load('AM13_data.mat');
   plot_traveltime_sr(D.S,D.R);
   or
   ant_pos=[D.S,D.R];
   plot_traveltime_sr(ant_pos);
 
   % 3D
   D=load('AM1234_data.mat');
   plot_traveltime_sr(D.S,D.R);