Calculate bearing between two decimal GPS coordinates (Arduino / C++)

Question

I am trying to calculate the bearing just like in this example: Calculate bearing between two decimal GPS coordinates , but my environment is Arduino.

I got the code translated (please see below), but I am having issues with the floating points. I need a higher resolution/precision.

Using these points:

double r1 = 9.935483816921979;
double r2 = -84.05334153306967;
double g1 = 9.936029735119176;
double g2 = -84.0532617256946;

I get these results:

8.194077303640654 // In the js code from the example
9.229920 // from my Arduino code

How can I get more precision?

// Here is my Arduino Code
double getBearing(double lat1,double lng1,double lat2,double lng2) {
  lat1 = radians(lat1);
  lng1 = radians(lng1);
  lat2 = radians(lat2);
  lng2 = radians(lng2);

  double dLng = lng2 - lng1;
  double dPhi = log(tan(lat2 / 2.0 + PI / 4.0) / tan(lat1 / 2.0 + PI / 4.0));

  if (abs(dLng) > PI){
    if (dLng > 0.0)
     dLng = -(2.0 * PI - dLng);
  else
    dLng = (2.0 * PI + dLng);
  }

  return fmod((degrees(atan2(dLng, dPhi)) + 360.0), 360.0); 
}

Answer 1

You can calculate your bearing with this function.

float bearing(float lat,float lon,float lat2,float lon2){

    float teta1 = radians(lat);
    float teta2 = radians(lat2);
    float delta1 = radians(lat2-lat);
    float delta2 = radians(lon2-lon);

    //==================Heading Formula Calculation================//

    float y = sin(delta2) * cos(teta2);
    float x = cos(teta1)*sin(teta2) - sin(teta1)*cos(teta2)*cos(delta2);
    float brng = atan2(y,x);
    brng = degrees(brng);// radians to degrees
    brng = ( ((int)brng + 360) % 360 ); 

    Serial.print("Heading GPS: ");
    Serial.println(brng);

    return brng;


  }

where variables are:

• lat = your current gps latitude.
• lon = your current gps longitude.
• lat2 = your destiny gps latitude.
• lon2 = your destiny gps longitude.