Determine the heading or azimuth angle of satellite Meteor M2

Question

I am working on a project Meteor decoder, where I need to calculate the pixel geolocations of the satellite image to draw map overlays. I have all the angles except the azimuth angle. I tried to calculate it from orbital elements, I took two relatively close coordinates at two different timestamp and calculated the angle between them. But this solution is not perfect.

Sample code for calculating every 10th pixel's geolocation, I hope it is clear:

void PixelGeolocationCalculator::calcPixelCoordinates()
{
    double angle;
    CoordGeodetic satOnGroundPrev;
    CoordGeodetic satOnGround;
std::vector<Eci> passList;

DateTime passEnd = DateTime(mPassStart).Add(mPassLength);

for(DateTime currentTime = mPassStart; currentTime <= passEnd; currentTime = currentTime.AddMicroseconds(PIXELTIME_MS * 10 * 1000))
{
    passList.push_back(mSgp4.FindPosition(currentTime));
}

std::vector<Eci>::const_iterator it = passList.begin();
std::vector<Eci>::const_iterator prevIt = passList.begin();
++it;

DateTime currentTime = mPassStart;
for (unsigned int i = 0 ; it != passList.end(); prevIt = it,  ++it, i++)
{
    satOnGroundPrev = Eci(currentTime, prevIt->Position(), prevIt->Velocity()).ToGeodetic();
    satOnGround = Eci(currentTime, it->Position(), it->Velocity()).ToGeodetic();
    currentTime = currentTime.AddMicroseconds(PIXELTIME_MS * 10 * 1000);

    angle = calculateBearingAngle(satOnGround, satOnGroundPrev);
    angle = degreeToRadian(90) - angle;

    for (int n = 79; n > -79; n--)
    {
        CoordGeodetic coordinate (los_to_earth(satOnGround, degreeToRadian((((mAlfa) / 79.0)) * n), 0, angle));
        mCoordinates.push_back(coordinate);
    }
}

}

Any better way to calculate this?