#
# stidata object
#
##  2003dec13   LAMA Memo 803 writeup version
#

# include 'stidata.g'
# sti := stidata()
# sti.setdata( rms=1.0, alpha=0.6 )
# sti.getphase( freq=230, baseline=[10,40,160], el=60 ) 
# sti.done()



stidata := subsequence () {

   private := [=];


   private.stifreq := 11.198;   #  site testing interferometer Frequency
   private.stibaseline := 300;  #  baseline length [m] of STI
   private.stiel := 30;   #  elevation angle of STI
   
   private.rms300 := 1.0; 		# degrees of phase at stifreq
   private.alpha := 0.58;	# structure function alpha

	
   self.done := function() {
        wider self, private;
        val self := F;
        val public := F;
        return T;
   }

   self.setdata := function( rms=1.0, alpha=0.58) {
     wider private;

     private.rms300 := rms;
     private.alpha := alpha;
     return T;
   }

# works on vector baseline;
   self.getphase := function ( freq=230, baseline=[300], el=60 ) {

      coeff := private.rms300 * freq / private.stifreq  /
               sqrt(1/sin(private.stiel/(180/pi)));

      phaseresid := sqrt(1/sin(el/(180/pi))) * coeff * ( baseline/private.stibaseline )^private.alpha; 

      return phaseresid;
   }


}