Rotating an ImageView like a compass (with the “north pole” set elsewhere)

Question

I\'m stumped regarding how to implement a \"personal compass\", ie a compass that points to a specific bearing instead of the standard \"north pole\"... unfortunatly, my cu

Answer 1

I spent about 40 hours one weekend trying to do this.

Pain in the butt, hopefully I can spare you that pain.

Ok, I am warning you, this is some ugly code. I was in a pinch to finish it, it has no naming schemes, but i tried to comment it as best as I could for you.

It was used to locate large piles of nuts laying out in fields for storage

Using the phones current latitude and longitude, the lat/lon of the destination, the compass sensor, and some algebra, I was able to calculate the direction to the destination.

Lat/lon and sensor readings are pulled from the MainApplication class

This is some of the code for arrow.class, which I used to draw an arrow on a canvas towards a direction.

    //The location you want to go to//
    //"Given North"
    double lat=0;
    double lon=0;
    //////////////////////////////////
    protected void onDraw(Canvas canvas) {

    //Sensor values from another class managing Sensor
    float[] v = MainApplication.getValues();

    //The current location of the device, retrieved from another class managing GPS
    double ourlat=  MainApplication.getLatitudeD();
    double ourlon=  MainApplication.getLongitudeD(); 

    //Manually calculate the direction of the pile from the device
    double a= Math.abs((lon-ourlon));
    double b= Math.abs((lat-ourlat));
    //archtangent of a/b is equal to the angle of the device from 0-degrees in the first quadrant. (Think of a unit circle)
    double thetaprime= Math.atan(a/b);
    double theta= 0;

    //Determine the 'quadrant' that the desired location is in
    //ASTC (All, Sin, Tan, Cos)  Determines which value is positive
    //Gotta love Highschool algebra

    if((latourlon)){//-+ 
        //theta is 180-thetaprime because it is in the 2nd quadrant
        theta= ((Math.PI)-thetaprime); 

        //subtract theta from the compass value retrieved from the sensor to get our final direction
        theta=theta - Math.toRadians(v[0]);

    }else if((latourlat)&&(lon>ourlon)){ //++
        //No change is needed in the first quadrant
        theta= thetaprime; 

        //subtract theta from the compass value retreived from the sensor to get our final direction
        theta=theta - Math.toRadians(v[0]);

    }else if((lat>ourlat)&&(lon

Hopefully you can manage to read my code... If I get time, I will make it a bit prettier.

If you need any explaining, let me know.

-MrZander