function [num,k]=get_seesate(xsg,ysg,zsg,xug,yug,zug,flag);

%*********************************
% ** % 得出可見星的編號及個數(shù)
% ** flag為系統(tǒng)標(biāo)志 gps:flag = 1;galileo: flag = 2; beidou:flag = 3 
% **********************************

switch flag
    case 1
        mm = 6;nn = 4;
    case 2
        mm = 3;nn = 9;
    case 3
        mm = 1;nn = 2;
end

dx=xsg-xug*ones(mm,nn);
dy=ysg-yug*ones(mm,nn);
dz=zsg-zug*ones(mm,nn);%衛(wèi)星與用戶的向量差
EL=atan(dz./sqrt((dx.^2)+(dy.^2)));%通過反正切求衛(wèi)星對于用戶的仰角
m=EL*360/(2*pi)>7.5*ones(mm,nn);%當(dāng)仰角大于7.5時.對應(yīng)6*4矩陣的該元素為1,否則為0
l=1:mm*nn;
l=reshape(l,nn,mm)';%將衛(wèi)星編號
num=[];
for i=1:mm;
    for j=1:nn;
        if m(i,j)==1;
            num=[num,l(i,j)];
        end
    end
end
k=length(num);
num=num(1,:);