apparentAzElSouth

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

  function d = apparentAzEl(d, includeError)

  functions that retracts the pointing model and refraction corrections to
  go from encoder az/el to sky az/el.

  d - data structure
  
  creates new subfield:
    d.antenna0.servo.apparent, which is [Nby4], where each column
    corresponds to :
    [apparentAzimuth, apparentElevation, error in fit for Az, error in fit
    for El];


aza is the apparent azimuth
ela is the apparent elevation
erraz is the error between the antenna coordinate recorder in the data and
what we get when we use the apparent position to start with for refraction
and pointing calcualtions
similarly for erralt

  CJC

%%%%%%%%%%%%%%%%%%%%%%%%%%%
 ogk edit 1:
 Changed the condition in the while loop to
 Azimuth Error > threshold -> mod(Azimuth Error,360)>threshold
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  sjcm Aug 10, 2011:  modified inputs so we don't report back the error in
  az/el automatically (which i don't think actually gets used anywhere);
  memory problem.  
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

0001 function d = apparentAzElSouth(d, includeError)
0002 
0003 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
0004 %
0005 %  function d = apparentAzEl(d, includeError)
0006 %
0007 %  functions that retracts the pointing model and refraction corrections to
0008 %  go from encoder az/el to sky az/el.
0009 %
0010 %  d - data structure
0011 %
0012 %  creates new subfield:
0013 %    d.antenna0.servo.apparent, which is [Nby4], where each column
0014 %    corresponds to :
0015 %    [apparentAzimuth, apparentElevation, error in fit for Az, error in fit
0016 %    for El];
0017 %
0018 %
0019 %aza is the apparent azimuth
0020 %ela is the apparent elevation
0021 %erraz is the error between the antenna coordinate recorder in the data and
0022 %what we get when we use the apparent position to start with for refraction
0023 %and pointing calcualtions
0024 %similarly for erralt
0025 %
0026 %  CJC
0027 %
0028 %%%%%%%%%%%%%%%%%%%%%%%%%%%%
0029 % ogk edit 1:
0030 % Changed the condition in the while loop to
0031 % Azimuth Error > threshold -> mod(Azimuth Error,360)>threshold
0032 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
0033 %  sjcm Aug 10, 2011:  modified inputs so we don't report back the error in
0034 %  az/el automatically (which i don't think actually gets used anywhere);
0035 %  memory problem.
0036 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
0037  
0038 if(nargin<2)
0039   includeError = 0;
0040 end
0041 
0042 
0043 %get the antenna coordinates that we start with
0044 azprime=d.antenna0.servo.az;
0045 elprime = d.antenna0.servo.el;
0046 maxitr=20;
0047 
0048 %lets just see what sort of correction we get at this antenna angle (AZ')-
0049 %if we assume the difference between AZ (apparent) and AZ'(antenna) is
0050 %small then we can use this number as a start approximation- here we have 3
0051 %coordinates Az (apparent AZ) Az' (antenna Az) AZ'' (meaningless azimuth
0052 %position calculated by applying a pointing and refraction correction to ...
0053 %    Az') and we
0054 %make the assumptio that Az-Az' is approximately Az'-Az''
0055 [azdoubleprime,eldoubleprime]=calcAzEl2South(azprime,elprime,d);
0056 
0057 %now we calculate what sort of offset we have, daz and del-note that this
0058 %offset is between AZ' and AZ''- ie daz=AZ'-AZ''- therefore to go back to
0059 %AZ we use the equation daz~=AZ-AZ' (using approximation) and therefore ...
0060 %    AZ=AZ'+daz
0061 
0062 daz=azprime-azdoubleprime;
0063 del=elprime-eldoubleprime;
0064 
0065 %Now we assume that the difference between the apparent and antenna
0066 %coordinates is small i.e that the same sort of correction would have been
0067 %found if we'd done the calculation on the apparent coordinates- defining
0068 %apparent coordinates as AZ and antenna coordinates as AZ' we have
0069 %daz = AZ-AZ' (not the difference and similarity (!!!) with the calculation
0070 %above
0071 % AZ=AZ'+daz
0072 
0073 azapp = azprime+daz;
0074 elapp = elprime+del;
0075 
0076 %So these are our first guesses for the apparent azimuth and elevation
0077 %values- they should be ok but lets just check by going from these values
0078 %back to the antenna values and comparing
0079 
0080 [azprime2,elprime2]=calcAzEl2South(azapp,elapp,d);
0081 
0082 errazprime = (azprime-azprime2);
0083 errelprime = (elprime-elprime2);
0084 
0085 maxazerr=max(abs(errazprime));
0086 maxelerr=max(abs(errelprime));
0087 vecazerr=[];
0088 vecelerr=[];
0089 a=isnan(daz);
0090 daz(a)=0;
0091 a=isnan(del);
0092 del(a)=0;
0093 %Now we iteratively adjust the Az (apparent coordinate) until it produces
0094 %the 'correct' AZ
0095 
0096 alen=length(daz);
0097 i=0;
0098 %while(((maxazerr >0.0001) || (maxelerr>0.0001)) && (i<maxitr))
0099  % i=i+1;
0100   %disp(['Iteration (max): ', num2str(i),'(',num2str(maxitr),')']);
0101 
0102 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
0103 % ogk edit 1: change while loop conditional statement to
0104 % mod(maxazerr,360)<...
0105 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
0106 while(((mod(maxazerr,360) >0.0001) || (maxelerr>0.0001)) && (i<maxitr))
0107   i=i+1;
0108   disp(['Iteration (max): ', num2str(i),'(',num2str(maxitr),')']);  
0109   [azprime2,elprime2]=calcAzEl2South(azapp,elapp,d);
0110   errazprime = wrap180(azprime - azprime2);
0111   errelprime = wrap180(elprime - elprime2);
0112   a=isnan(errazprime);
0113   errazprime(a)=0;
0114   a=isnan(errelprime);
0115   errelprime(a)=0;
0116   
0117   maxazerr=max(abs(errazprime));
0118   maxelerr=max(abs(errelprime));
0119   daz = daz + errazprime;
0120   del = del + errelprime;
0121   azapp= wrap360(azprime+daz);
0122   elapp = wrap360(elprime+del);
0123   vecazerr=[vecazerr maxazerr];
0124   vecelerr=[vecelerr maxelerr];
0125 %end
0126 end
0127 
0128 if i>=maxitr
0129     %Error handling in case the removal of the pointing correction isn't
0130     % working
0131     error('Apparent Az/El not converging')
0132 end
0133 %might need some error checking here but otherwise
0134 
0135 erraz=errazprime;
0136 errel=errelprime;
0137 aza=azapp;
0138 ela=elapp;
0139 
0140 if(includeError)
0141   d.antenna0.servo.apparent = [aza ela erraz errel];
0142 else
0143   d.antenna0.servo.apparent = [aza ela]; 
0144 end
0145 
0146 return;