CODEWITHSUNDEEP
androidlocationcompass-geolocationmylocationoverlay
droid8421
droid8421

Reputation: 895

Make MyLocationOverlay compass point to a particular location

I'm trying to make MyLocationOverlay compass to point to a particular location. I want to show a direction from current user's location to a given location. So far I've managed to calculate a direction and pass it to MyLocationOverlay. But the compass arrow starts pointing to different locations chaotically. Sometimes it points to the right direction but usually it shows complete nonsense.

Is there a way to make the compass work as it should?

This is how I calculate the direction in my activity 

    @Override
    public void onSensorChanged(SensorEvent event) {
        if(location != null && carOverlay.size() > 0 
                && !map.getUserOverlay().isPointingToNorth()) {

            float azimuth = event.values[0];
            azimuth = azimuth * 180 / (float) Math.PI;
            GeomagneticField geoField = new GeomagneticField(
                    Double.valueOf(location.getLatitude()).floatValue(),
                    Double.valueOf(location.getLongitude()).floatValue(),
                    Double.valueOf(location.getAltitude()).floatValue(),
                    System.currentTimeMillis());
            azimuth += geoField.getDeclination();

            GeoPoint point = carOverlay.getItem(0).getPoint();
            Location target = new Location(provider);
            float lat = (float) (point.getLatitudeE6() / 1E6f);
            float lon = (float) (point.getLongitudeE6() / 1E6f);
            target.setLatitude(lat);
            target.setLongitude(lon);

            float bearing = location.bearingTo(target);
            float direction = azimuth - bearing;

            map.getUserOverlay().putCompassDirection(direction);
        }
    }

This is the overriden method in my custom overlay 

@Override
    protected void drawCompass(Canvas canvas, float bearing) {
        if(pointToNorth) {
            super.drawCompass(canvas, bearing);
        }
        else {
            super.drawCompass(canvas, compassDirection);
        }

    }

Upvotes: 0

Views: 3186

Answers (1)

Rafael T
Rafael T

Reputation: 15669

Why do you calculate your "bearing/azimuth" yourself? MyLocationOverlay hold the Method getOrientation() to give you the azimuth. I would definetly leave onSensorChanged untouched, and let the MyLocationOverlay calculate this for you. Normally to draw your Compass correct you just have to call enableCompass()

Upvotes: 0

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