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OT - Adding Roll & pitch to sat dish pointing
Message #1 Posted by Giuseppe Marullo on 22 Jan 2011, 6:34 p.m.

Hi all, I don't know where to look so I am asking for some assistance here.

A friend of mine asked help to develop a automagic satellite dish tracker (stationary).

Basically, we put togheter compass and GPS data to move a dish automatically to receive HotBird.

We have tested the basic formulas and they seems okay against the tables provided for latitude and longitude.

Now I would like to add pitch and roll of the truck in the equations to account for small angles that could lead to errors.

I have roll&pitch from 2 accelerometers in degrees resolution -+1 degrees increment (or I could access raw accelerometer data).

These are the formulas we are using:

PosLat = (2*M_PI*PosLat) / 360.0; // truck latitude to radians PosLong = (2*M_PI*PosLong) / 360.0; // truck longitude to radians SatLong = (2*M_PI*SatLong) / 360.0; // sat longitude to radians

v1 = 6.612 * cos(PosLat)*cos(PosLong-SatLong)-1;

v2 = 6.612 * sqrt( 1-(pow(cos(PosLat),2)) * pow((cos(PosLong- SatLong)),2));

SatElevation = atan(v1/v2); SatAzimuth = M_PI + atan( tan(PosLong-SatLong) / sin(PosLat) ); SatPolarization = -atan( sin(PosLong-SatLong) /tan(PosLat) );


SatElevation = (SatElevation * 360.0) / (2*M_PI); // sat elevation in deg SatAzimuth = (SatAzimuth * 360.0) / (2*M_PI); // sat azimuth in deg

How could I modify the formulas to account for pitch & roll of the truck? Could you eventually point me to any site that could explain to me easily how to achieve this?


Giuseppe Marullo PS: remove nospam to reply

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