问题描述:

I'm trying to make a compass that points to a custom location in a Unity program. However it's completely off, it points in generally the wrong direction and I can't quite seem to figure out what is wrong with my logic.

I'm using the curved geometry bearing equation from here: http://www.yourhomenow.com/house/haversine.html

- Get current location.
- Calculate bearing from current location to target location.
Rotate screen compass relative to true north.

`// Calculate bearing between current location and target location`

// Get current GPS location

float lat1 = Input.location.lastData.latitude;

float lon1 = Input.location.lastData.longitude;

float lat2 = TargetLatitude;

float dLon = TargetLongitude - lon1;

// Calculate bearing

var y = Mathf.Sin(dLon) * Mathf.Cos(lat2);

var x = Mathf.Cos(lat1) * Mathf.Sin(lat2) -

Mathf.Sin(lat1) * Mathf.Cos(lat2) * Mathf.Cos(dLon);

var brng = ((Mathf.Atan2(y, x)*(180.0f/Mathf.PI)) + 360.0f) % 360.0f;

Dump.text = brng.ToString();

// Rotate the to target location relative to north. Z axis pointing out of screen.

transform.eulerAngles = new Vector3(0, 0, Mathf.MoveTowardsAngle(transform.localEulerAngles.z, Input.compass.trueHeading + brng, COMPASS_MAXDELTA));

If I remove the bearing offset in that code, it points north enough for a digital compass.

Make sure that all of your angles are in radians rather than degrees.

Using `Mathf.Deg2Rad`

in cases such as `Mathf.Sin(dLon * Mathf.Deg2Rad)`

should yield the correct result. The Haversine formula only works for angles in radians.