获取 farLat、farLng 和 nearLat、nearLng 之间的距离

Question

我越来越远 LatLng 如下：

mFarLeft = mMapView.getProjection().getVisibleRegion().farLeft;
mFarRight = mMapView.getProjection().getVisibleRegion().farRight;
mNearLeft = mMapView.getProjection().getVisibleRegion().nearLeft;
mNearRight = mMapView.getProjection().getVisibleRegion().nearRight;

现在，如何计算这个远点和近点之间的距离？
是否有任何方法可以获取以公里和英尺为单位的距离？

Answer 1

字段farLeft、farRight等实际上是LatLng对象，根据Androiddocumentation。但是，有一个字段 latLngBounds 表示包括可见区域的最小边界框。这个边界对象本身有两个 LatLng 字段，用于框的东北角和西南角。使用 Haversine 公式，我们可以计算这个盒子的角之间的距离。例如，如果您想计算边界框的高度，我们可以尝试：

public static double haversine(double lat1, double lon1, double lat2, double lon2) {
    double dLat = Math.toRadians(lat2 - lat1);
    double dLon = Math.toRadians(lon2 - lon1);
    lat1 = Math.toRadians(lat1);
    lat2 = Math.toRadians(lat2);

    double a = Math.pow(Math.sin(dLat / 2),2) + Math.pow(Math.sin(dLon / 2),2) * Math.cos(lat1) * Math.cos(lat2);
    double c = 2 * Math.asin(Math.sqrt(a));
    return 6372.8 * c;   // in kilometers
    // if you want to return feet, then use 6372.8 * 3280.84 instead
}

public static void main(String[] args) {
    LatLng ne = mMapView.getProjection().getVisibleRegion().latLngBounds.northeast;
    LatLng sw = mMapView.getProjection().getVisibleRegion().latLngBounds.southwest;
    double latLow = sw.latitude;
    double latHigh = ne.latitude;
    double longitude = sw.longitude;

    // now compute the "height" of the bounding box
    // note that the longitude value is the same
    double height = haversine(latLow, longitude, latHigh, longitude);
}

Answer 2

Google 为地图提供实用程序库，除其他外，

Calculate distances, areas and headings via spherical geometry

Using the spherical geometry utilities in SphericalUtil, you can compute distances, areas, and headings based on latitudes and longitudes. Here are some of the methods available in the utility:

computeDistanceBetween() – Returns the distance, in meters, between two latitude/longitude coordinates.

computeHeading() – Returns the bearing, in degrees, between two latitude/longitude coordinates.

computeArea() – Returns the area, in square meters, of a closed path on the Earth.

interpolate() – Returns the latitude/longitude coordinates of a point that lies a given fraction of the distance between two given points. You can use this to animate a marker between two points, for example.

Refer to the reference documentation for a full list of methods in the utility.

该库在 Maven Central 上可用。

dependencies {
    compile 'com.google.maps.android:android-maps-utils:0.5+'
}

来源：https://developers.google.com/maps/documentation/android-api/utility/

获取 farLat、farLng 和 nearLat、nearLng 之间的距离

Getting distance between farLat, farLng and nearLat, nearLng

android

google-maps

latitude-longitude

Calculate distances, areas and headings via spherical geometry