我正在编写Android应用并集成GoogleMapsV2 API。我在地图上的锚点附近的各个位置都有一系列标记。
我希望这些标记能够逐渐收敛到锚点的位置。
我有一个循环运行，它将调用每个标记B，并从B的位置计算到锚A的方位。然后我计算沿着该方位的固定距离的目标坐标并更新。
以下是两个功能（取自叠加帖子和GeoMapping网站的合并，用于完整披露）我正在使用：
public double calcBearing(double lat1, double lon1, double lat2, double lon2){
double longitude1 = lon1;
double longitude2 = lon2;
double latitude1 = Math.toRadians(lat1);
double latitude2 = Math.toRadians(lat2);
double longDiff= Math.toRadians(longitude2-longitude1);
double y= Math.sin(longDiff)*Math.cos(latitude2);
double x=Math.cos(latitude1)*Math.sin(latitude2)-Math.sin(latitude1)*Math.cos(latitude2)*Math.cos(longDiff);
double calcBearing = (Math.toDegrees(Math.atan2(y, x))+360)%360;
return calcBearing;
}
public Coordinate calcCoordFromPointBearing(double lat1, double lon1, double bearing, double distance){
double rEarth = 6371.01; // Earth's average radius in km
double epsilon = 0.000001; // threshold for floating-point equality
double rLat1 = deg2rad(lat1);
double rLon1 = deg2rad(lon1);
double rbearing = deg2rad(bearing);
double rdistance = distance / rEarth;
double rlat = Math.asin( Math.sin(rLat1) * Math.cos(rdistance) + Math.cos(rLat1) * Math.sin(rdistance) * Math.cos(rbearing) );
double rlon;
if (Math.cos(rlat) == 0 || Math.abs(Math.cos(rlat)) < epsilon) // Endpoint a pole
rlon=rLon1;
else
rlon = ( (rLon1 - Math.asin( Math.sin(rbearing)* Math.sin(rdistance) / Math.cos(rlat) ) + Math.PI ) % (2*Math.PI) ) - Math.PI;
double lat = rad2deg(rlat);
double lon = rad2deg(rlon);
return new Coordinate(lat,lon);
}
private double deg2rad(double deg) {
return (deg * Math.PI / 180.0);
}
private double rad2deg(double rad) {
return (rad * 180.0 / Math.PI);
}
简而言之，我相信我已经搞砸了上述计算。我看到的行为是不规则地移动的标记，并且高频率朝向两个轴承：90和270.因此，它们倾向于远离我的锚而不是朝向它。
有人能帮助我发现错误吗？我正在向度量函数和坐标计算函数传递度数，但是我将它们立即转换为算法的弧度并返回到其他地方使用的度数。
[UPDATE：
大多数代码来自这个例子：
Calculating coordinates given a bearing and a distance
在我看来，输出经度被标准化为-180到180，我在360度空间上绘图，导致输出前进到轴承90和270.有关trig数学的任何建议修改此问题需要更改吗？]
答案 0 :(得分：3)
可能需要360.0
double calcBearing = (Math.toDegrees(Math.atan2(y, x))+360.0)%360.0;
这有点回答here
你还有另一个问题。你不考虑地图中的任何倾斜。为什么不用像素动画。不会有过多的曲率变形。你需要做的是获得标记的像素位置。添加标记时，您必须保存latlon，或者必须使用.setAnchor添加标记，这样可以提供像素偏移量。如果您有标记放置的latlon，那么您可以得到点。
LatLon ll;
Point p = mMap.getProjection().toScreenLocation(ll);
然后您可以使用这样的代码来设置标记的动画。我通过插入y轴使标记反弹到下面。你必须插入两个轴。
final Handler handler = new Handler();
final long start = SystemClock.uptimeMillis();
final long duration = 2500;
final Interpolator interpolator = new BounceInterpolator();
handler.post(new Runnable() {
@Override
public void run() {
long elapsed = SystemClock.uptimeMillis() - start;
float t = Math.max(
1 - interpolator.getInterpolation((float) elapsed
/ duration), 0);
marker.setAnchor(0.5f, 1.0f + 6 * t);
if (t > 0.0) {
// Post again 16ms later.
handler.postDelayed(this, 16);
}
}
});
以上代码来自question.我对您在使用上述方法时遇到的任何性能问题表示歉意。但你仍然可以使用像素位置来进行更传统的动画制作。
我在另一个程序中使用了几乎相同的公式，在该程序中，我根据位置方位和速度为地图设置动画以移动到预期位置。公式与您的公式略有不同。我把它从here抬起来，换成了更长的名字。
// Define the callback method that receives location updates
@Override
public void onLocationChanged(Location location) {
// Given the bearing, speed, and current location
// calculate what the expected location is traveling for an
// interval that is slightly larger than two times fastest interval of
// the location provider and animate the map movement to the
// expected location over the same slightly larger interval.
// In Theory by using an interval that is slightly larger
// than two times fastest interval of the location provider for the
// animation length a new animation will start before the
// currently running animation finishes. This should ensure a
// smooth animation of the map while traveling under most
// circumstances.
// Negative acceleration (braking)
// should have acceptable map animation because the map
// animation in theory never finishes.
// Note longer intervals, large negative accelerations, just
// braking at the start of an interval may result in the map moving
// backwards. But it will still be animated.
// Some handhelds might not be able to keep up
// TODO CHECK THE age of the location
// location.getSpeed() =meters/second
// interval 1/1000 seconds
// distance in radians km/6371
// changed.
// (location.getSpeed()m/s)(1/1000 interval seconds)( 1/1000 km/m)
// (1/6371 radians/km) = radians/6371000000.0
double expectedDistance = location.getSpeed() * expectedDistMultiplier;
// latitude in Radians
double currentLatitude = Math.toRadians(location.getLatitude());
// longitude in Radians
double longitude1 = Math.toRadians(location.getLongitude());
double bearing;
bearing = (location.hasBearing()) ? Math.toRadians(location
.getBearing()) : 0;
// calculate the expected latitude and longitude based on staring
// location
// , bearing, and distance
double expectedLatitude = Math.asin(Math.sin(currentLatitude)
* Math.cos(expectedDistance) + Math.cos(currentLatitude)
* Math.sin(expectedDistance) * Math.cos(bearing));
double a = Math.atan2(
Math.sin(bearing) * Math.sin(expectedDistance)
* Math.cos(currentLatitude),
Math.cos(expectedDistance) - Math.sin(currentLatitude)
* Math.sin(expectedLatitude));
double expectedLongitude = longitude1 + a;
expectedLongitude = (expectedLongitude + 3 * Math.PI) % (2 * Math.PI)
- Math.PI;
// convert to degrees for the expected destination
double expectedLongitudeDestination = Math.toDegrees(expectedLongitude);
double expectedLatitudeDestination = Math.toDegrees(expectedLatitude);
// log everything for testing.
Log.d("Location", "Bearing in radians" + bearing);
Log.d("Location", "distance in km" + expectedDistance);
Log.d("Location", "Current Latitude = " + location.getLatitude()
+ " Current Longitude = " + location.getLongitude());
Log.d("Location", "New Latitude = " + expectedLatitudeDestination
+ " New Longitude = " + expectedLongitudeDestination);
// build a camera update to animate positioning map to the expected
// destination
LatLng ll = new LatLng(expectedLatitudeDestination,
expectedLongitudeDestination);
CameraPosition.Builder cb = CameraPosition.builder()
.zoom(mMap.getCameraPosition().zoom)
.bearing(mMap.getCameraPosition().bearing)
.tilt(mMap.getCameraPosition().tilt).target(ll);
if (location.hasBearing()) {
cb.bearing(location.getBearing());
}
CameraPosition camera = cb.build();
CameraUpdate update = CameraUpdateFactory.newCameraPosition(camera);
mMap.animateCamera(update, interval, this);
}