--------------------------------------------------------------------
cosined function cosine direction transformation
convert lon & lat to cosine direction
and visa versa. UNITS are in radians!
input : - column matrix, with 2 or 3 colums.
if 2 colums are given then, the first column
is longitude and the second is latitude.
and the cosine direction are returned.
if three columns are given, then they suppose to
be the cosine direction, and the longitude
and latitude are returned.
output : - cosine direction or longitude and latitude.
By Eran O. Ofek July 1999
--------------------------------------------------------------------0001 function Res=cosined(Vec); 0002 %-------------------------------------------------------------------- 0003 % cosined function cosine direction transformation 0004 % convert lon & lat to cosine direction 0005 % and visa versa. UNITS are in radians! 0006 % input : - column matrix, with 2 or 3 colums. 0007 % if 2 colums are given then, the first column 0008 % is longitude and the second is latitude. 0009 % and the cosine direction are returned. 0010 % if three columns are given, then they suppose to 0011 % be the cosine direction, and the longitude 0012 % and latitude are returned. 0013 % output : - cosine direction or longitude and latitude. 0014 % By Eran O. Ofek July 1999 0015 %-------------------------------------------------------------------- 0016 if (length(Vec(1,:))==2), 0017 Alpha = Vec(:,1); 0018 Delta = Vec(:,2); 0019 Res = zeros(length(Vec(:,1)),3); 0020 Res(:,1) = cos(Alpha).*cos(Delta); 0021 Res(:,2) = sin(Alpha).*cos(Delta); 0022 Res(:,3) = sin(Delta); 0023 elseif (length(Vec(1,:))==3), 0024 L1 = Vec(:,1); 0025 L2 = Vec(:,2); 0026 L3 = Vec(:,3); 0027 Res = zeros(length(Vec(:,1)),2); 0028 Res(:,1) = atan2(L2,L1); % Alpha 0029 SLL = sqrt(L1.^2+L2.^2); 0030 I0 = find(SLL==0); 0031 In0 = find(SLL~=0); 0032 Res(In0,2) = atan(L3(In0)./SLL(In0)); % Delta 0033 Res(I0,2) = sign(L3(I0)).*pi./2; % Delta 0034 else 0035 error('only 2/3 columns are allowed'); 0036 end