Calculating midpoint from two coordinates

问题

I was having some problem when trying to find the mid point between two point. Here is the part where I get the shortest distance between two point:

                    double distance = 0;
                    double minDistance = Double.MAX_VALUE;

                    convertedHotSpotGeomList = RetrieveHotSpotAsyncTask.convertedHotSpotGeom;
                    LatLng[] minPoints = new LatLng[2]; 

                    for(int i = 0; i < convertedHotSpotGeomList.size(); i++){
                        LatLng point1 = new LatLng(convertedHotSpotGeomList.get(i).getY(),   convertedHotSpotGeomList.get(i).getX());                                 
                        LatLng point2 = new LatLng(convertedHotSpotGeomList.get(++i).getY(), convertedHotSpotGeomList.get(++i).getX());

                        distance = calculateDistance(point1, point2);
                        if(distance < minDistance){
                            minDistance = distance;
                            minPoints[0] = point1;
                            minPoints[1] = point2;
                        }
                    }

                    // Finish all the comparison and draw the circles
                    if(minPoints[0]!=null && minPoints[1] !=null){
                        CircleOptions circleOptions = new CircleOptions()
                            .center(minPoints[0])
                            .radius(1000)
                            .fillColor(Color.argb(95, 178, 30, 37))
                            .strokeColor(Color.TRANSPARENT);
                        CircleOptions circleOptions1= new CircleOptions()
                            .center(minPoints[1])
                            .radius(1000)
                            .fillColor(Color.argb(95, 88, 130, 37))
                            .strokeColor(Color.TRANSPARENT);

                        googleBasemap.addCircle(circleOptions);
                        googleBasemap.addCircle(circleOptions1);

                        midPoint(minPoints[0].latitude,minPoints[0].longitude,minPoints[1].latitude,minPoints[1].longitude);
                    }
                }

And then from the center point of the two circles I drawn, I am calling this method to get the midpoint:

private void midPoint(double lat1,double lon1,double lat2,double lon2){
    double dLon = Math.toRadians(lon2 - lon1);

    lat1 = Math.toRadians(lat1);
    lat2 = Math.toRadians(lat2);
    lon1 = Math.toRadians(lon1);

    double Bx = Math.cos(lat2) * Math.cos(dLon);
    double By = Math.cos(lat2) * Math.sin(dLon);
    double lat3 = Math.atan2(Math.sin(lat1) + Math.sin(lat2), Math.sqrt((Math.cos(lat1) + Bx) * (Math.cos(lat1) + Bx) + By * By));
    double lon3 = lon1 + Math.atan2(By, Math.cos(lat1) + Bx);

    Log.i("LAT", String.valueOf(lat3));
    Log.i("LON", String.valueOf(lon3));
    CircleOptions circleOptions = new CircleOptions()
    .center(new LatLng(lon3, lat3))
    .radius(1000)
    .fillColor(Color.argb(95, 178, 30, 137))
    .strokeColor(Color.TRANSPARENT);

    googleBasemap.addCircle(circleOptions);
}

At the midpoint, I wanted to draw another circle onto the google map. However, when I print out the lat and lng for the mid point, I am getting this:

LAT 0.02512664 LON 1.811859

From what I've known, the coordinate of google map should be in 103. , 1. . I guess it's because the format is different and that's why the third circle is not coming out. Any ideas?

Thanks in advance.

回答1:

 double lat3 = Math.atan2(Math.sin(lat1) +...
 double lon3 = lon1 + Math.atan2(By, Math.cos(lat1) + Bx);

This returns radians. Go to degrees:

double latdeg = Math.toDegrees(lat3);
double londeg = Math.toDegrees(lon3);


103.81187377279383
1.4396504253445948

来源：https://stackoverflow.com/questions/28282578/calculating-midpoint-from-two-coordinates