plazitim.m

Sky lab calculate position of satellite in GNSS systems and calculate elevation and azimuth them and

function plazitim (eph,tsat,azim,elev,cutoff)
%PLAZITIM: Plot azimuth vs time
%
% The function create a plot showing the azimuth of GPS satellites
% as a function of time. Only satellites above the cutoff-angle are
% displayed.
%
% Syntax:
%    plazitim (eph,tsat,azim,elev,cutoff);
%
% Input arguments:
%    eph    - Ephemerides
%    tsat   - Time (secs)
%    azim   - Azimuth for each satellite
%    elev   - Elevation for each satellite
%    cutoff - Cutoff elevation
%
% Output arguments:
%    none

% ----------------------------------------------------------------------
% File.....: pleletim.m
% Date.....: 29-APR-1999
% Version..: 1.0
% Author...: Peter Joosten
%            Mathematical Geodesy and Positioning
%            Delft University of Technology
% ----------------------------------------------------------------------

% --------------------------------------
% --- Create the figure, set options ---
% --------------------------------------

h = figure('Units','normalized', ...
	   'Position',[0.2 0.5 0.6 0.3], ...
	   'Color',[0 0 0], ...
	   'Name','Azimuth vs. time', ...
	   'NumberTitle','off');

h = axes ('Units','normalized', ...
	  'Position',[0.05 0.10 0.90 0.80], ...
	  'Color',[0 0 0], ...
	  'XColor',[1 1 1], ...
	  'YColor',[1 1 1], ...
	  'Xgrid','on', ...
	  'Ygrid','on', ...
	  'Box','on');

hold on;

% -----------------------------------------
% --- Limits, grid, labels and such ... ---
% -----------------------------------------

xlabel ('Time [sec]');
ylabel ('Azimuth (deg)');

set (gca,'Xlim',[min(tsat) max(tsat)]);
set (gca,'Ylim',[0 360]);
plot ([min(tsat) max(tsat)],[cutoff cutoff],'w:');

% -------------------
% --- Actual plot ---
% -------------------

lcol = get(gca,'ColorOrder');

for i = 1:size(eph,1);

  idx1 = find(elev(i,:)>cutoff);
  
  if ~isempty(idx1);
    
    idx2 = [0 (find (idx1(1:length(idx1)-1) ~= idx1(2:length(idx1))-1)) length(idx1)];
    idx3 = find (abs(azim(i,idx1(1:length(idx1)-1))-(azim(i,idx1(2:length(idx1)))))>180);
    if ~isempty(idx3); idx2 = sort ([idx2 idx3]); end;
    
    for j = 1:length(idx2)-1

      h = plot (tsat(idx1(idx2(j)+1):idx1(idx2(j+1))), ...
		azim(i,idx1(idx2(j)+1):idx1(idx2(j+1))));
      set (h,'LineStyle','-');
      set (h,'LineWidth',2);
      set (h,'Color',lcol(mod(i,size(lcol,1))+1,:));
      
      tx = tsat(idx1(round(mean([idx2(j) idx2(j+1)]))));
      ty = azim(i,idx1(round(mean([idx2(j) idx2(j+1)]))))+3;
      h  = text(tx,ty,num2str(eph(i,1)));
      set (h,'Color',lcol(mod(i,size(lcol,1))+1,:));
      
    end;

  end
  
end;

% ----------------------
% --- End of routine ---
% ----------------------