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Wednesday, January 30, 2013

ES Elevation Angle Calculate Using MATLAB

Elevation angle E is the angle through which antenna must be turned to the direction of the satellite in vertical plane. To define the Earth Station (ES) elevation angle, we have to calculate the  ES position parameters such as the Earth Station Longitude (Les), Satellite Longitude (Ls) and Earth Station Latitude (lat). Beside that there are several fix parameter that using to get the ES Elevation degree, like Re= Radius of Earth = 6378 km, Ro=altitude of the geostationary satellite= 35,768 km. From this we can find E with formulas:


Noted, where cos f =cos (L)x cos (lat), and value of L equal with absolute value from Les-Ls. So from that information we can find value of E using MATLAB with this source code:


function Elv = satelev(lat,lgtd)
Re=6378; %Radius Bumi
Ro=35786; %Ketinggian Altitude satelit Pada Orbit Geostasioner
a=lat*(pi/180); %latitude stasiun bumi (lintang)
b=lgtd*(pi/180); %Selisih longitude satelit (bujur)
Elv=(atan(((cos(a)*cos(b))-(Re/(Re+Ro)))/((1-(cos(a)*cos(b))^2)^(1/2))))*(180/pi);
end

save this function to satelev.m (this matlab file). You have to know, This program is a function program, so when you want to use it. you have to declare the latitude of your ES and the value of L, using this source code
lgtd=value of lgtd;
lat=value of lat;

after that you can run the function and find the value with this source code
E= satelev(lat,lgtd);

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