Delta_t = 360;
x = 0:(Delta_t):24*3600;
len = length(x);
for n = 1:len      
   y19(n) = isSatelliteVisiable([60 -45],[55 296 26562000 0.01 331 254],x(n)) ;   
   y17(n) = isSatelliteVisiable([60 -45],[55 120 26562000 0.01 73 146],x(n));
   y16(n) = isSatelliteVisiable([60 -45],[55 178 26562000 0.01 164 82],x(n)) ;
end
 plot(x,y19);
 hold on;
 plot(x,y17+0.01,'r');
 plot(x,y16+0.02,'g');
 axis([0 1.2e5 -0.5 1.5]); 
 ratio16 = sum(y16)/length(y16);
 ratio17 = sum(y17)/length(y17);
 ratio19 = sum(y19)/length(y19);
 str16 = num2str(ratio16);
 str17 = num2str(ratio17);
 str19 = num2str(ratio19);
 text(0.15e5,1.3,['16號衛星可見率 ' str16 ' .']);
 text(0.15e5,1.2,['17號衛星可見率 ' str17 ' .']);
 text(0.15e5,1.1,['19號衛星可見率 ' str19 ' .']);