%
% S  = surfbet2outcrops(TRACER,LIMITS,LAT,LONG)
%
% This function computes the horizontal surface between two outcrops,
% given fixed limits eastward, westward and southward.
%
% TRACER = TRACER(LAT,LONG) : surface tracer variable in 2D
% LIMITS = [OUTCROP1 OUTCROP2 MAX_LAT1 MAX_LAT2 MAX_LONG1 MAX_LONG2]
%          : limit's values (MAX_LAT2 is used only if
%            the outcrop's surfaces reach them).
% LAT                             : latitude axis (1D), degrees northward
% LONG                            : longitude axis (1D), degrees east
% S                               : single surface value (m^2)
%
% 06/14/2006
% gmaze@mit.edu
% 


function varargout = surfbet2outcrops(TRACER,LIMITS,LAT,LONG)


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% PRE-PROCESS and ERROR CHECK %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
pv_checkpath

% Check number of input:
if nargin ~= 4
  help surfbet2outcrops.m
  error('surfbet2outcrops.m : Wrong number of parameters')
  return
end %if
  
% Check dimensions:
n = size(TRACER);
if length(n)==2
  [ny nx] = size(TRACER);
  if ny~=length(LAT) | nx~=length(LONG)
     help surfbet2outcrops.m
     error('surfbet2outcrops.m : Axis must have same dimensions than TRACER field');
     return
  end %if
else
  help surfbet2outcrops.m
  error('surfbet2outcrops.m : TRACER must be a 2D field')
  return
end %if

% Ensure that axis are of dim: (1,N) and well sorted (increasing values):
a=size(LAT);
if a(1) ~= 1,  LAT=LAT'; end 
S = sort(LAT);
if S ~= LAT
  help surfbet2outcrops.m
  error('surfbet2outcrops.m : LAT must be increasing values')
  return
end %if
a=size(LONG);
if a(1) ~= 1,  LONG=LONG'; end 
S = sort(LONG);
if S ~= LONG
  help surfbet2outcrops.m
  error('surfbet2outcrops.m : LONG must be increasing values')
  return
end %if

% LIMITS definition:
if length(LIMITS) ~= 6
  help surfbet2outcrops.m
  error('surfbet2outcrops.m : LIMITS must contains 6 values')
  return
end %if
OUTCROPS = sort( LIMITS(1:2) );
LAT_MAX  = sort( LIMITS(3:4) );
LONG_MAX = sort( LIMITS(5:6) ); 


  
%%%%%%%%%%%%%%%%%%%
% COMPUTE SURFACE %
%%%%%%%%%%%%%%%%%%%
% It's computed as the difference between the northern outcrop surface
% and the southern outcrop one.
[S1 S1mat dS1] = subfct_getsurf(TRACER,LAT,LONG,[OUTCROPS(1) LAT_MAX LONG_MAX]);
[S2 S2mat dS2] = subfct_getsurf(TRACER,LAT,LONG,[OUTCROPS(2) LAT_MAX LONG_MAX]);


% Then:
S = max(S1,S2)-min(S1,S2);


% Last we determine the outcrop surface limits:
S1mat = abs(S1mat - 1);
Smat  = (S1mat + S2mat)./2;
Smat(find(Smat<1)) = 0;
Smat = logical(Smat);




%%%%%%%%%%%
% OUTPUTS %
%%%%%%%%%%%
switch nargout
 case {0 , 1}
  varargout(1) = {S};
 case 2
  varargout(1) = {S};
  varargout(2) = {Smat};
 case 3
  varargout(1) = {S};
  varargout(2) = {Smat};
  varargout(3) = {dS1};
end %switch nargout