Android: How do I set the zoom level of map view to 1 km radius around my current location?

although this answer is logical and i find it working but the results are not accurate i dont know why but i tired this approach and this technique is far more accurate.

1) Make a circle on object with desired radius

Circle circle = mGoogleMap.addCircle(new CircleOptions().center(new LatLng(latitude, longitude)).radius(getRadiusInMeters()).strokeColor(Color.RED));           
        circle.setVisible(true);
        getZoomLevel(circle);

2) Pass that object to this function and set the zoom level
Here’s a link

public int getZoomLevel(Circle circle) {
if (circle != null){
    double radius = circle.getRadius();
    double scale = radius / 500;
    zoomLevel =(int) (16 - Math.log(scale) / Math.log(2));
}
return zoomLevel;
}

The following code is what ended up using. Given the screen width and the fact that at zoom level 1 the equator of Earth is 256 pixels long and every subsequent zoom level doubles the number of pixels needed to represent earths equator, the following function returns the zoom level where the screen will show an area of 2Km width.

private int calculateZoomLevel(int screenWidth) {
    double equatorLength = 40075004; // in meters
    double widthInPixels = screenWidth;
    double metersPerPixel = equatorLength / 256;
    int zoomLevel = 1;
    while ((metersPerPixel * widthInPixels) > 2000) {
        metersPerPixel /= 2;
        ++zoomLevel;
    }
    Log.i("ADNAN", "zoom level = "+zoomLevel);
    return zoomLevel;
}

I ended up using the utils from:

https://github.com/googlemaps/android-maps-utils

I extracted the class from the lib, so you don’t need the whole library.
Instead of setting zoom level, you use bounds. The result is the same.

Code to show exactly 1 kilometer:

animateToMeters(1000);

private void animateToMeters(int meters){
    int mapHeightInDP = 200;
    Resources r = getResources();
    int mapSideInPixels = (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, mapHeightInDP, r.getDisplayMetrics());

    LatLng point = new LatLng(0, 0);
    LatLngBounds latLngBounds = calculateBounds(point, meters);
    if(latLngBounds != null){
        cameraUpdate = CameraUpdateFactory.newLatLngBounds(latLngBounds, mapSideInPixels, mapSideInPixels, MARKER_BOUNDS);
        if(mMap != null)
            mMap.animateCamera(cameraUpdate); 
    }
}

private LatLngBounds calculateBounds(LatLng center, double radius) {
    return new LatLngBounds.Builder().
      include(SphericalUtil.computeOffset(center, radius, 0)).
      include(SphericalUtil.computeOffset(center, radius, 90)).
      include(SphericalUtil.computeOffset(center, radius, 180)).
      include(SphericalUtil.computeOffset(center, radius, 270)).build();
}

The class extracted (slightly changed) from the lib:

public class SphericalUtil {

    static final double EARTH_RADIUS = 6371009;

    /**
     * Returns hav() of distance from (lat1, lng1) to (lat2, lng2) on the unit sphere.
     */
    static double havDistance(double lat1, double lat2, double dLng) {
        return hav(lat1 - lat2) + hav(dLng) * cos(lat1) * cos(lat2);
    }

    /**
     * Returns haversine(angle-in-radians).
     * hav(x) == (1 - cos(x)) / 2 == sin(x / 2)^2.
     */
    static double hav(double x) {
        double sinHalf = sin(x * 0.5);
        return sinHalf * sinHalf;
    }

    /**
     * Computes inverse haversine. Has good numerical stability around 0.
     * arcHav(x) == acos(1 - 2 * x) == 2 * asin(sqrt(x)).
     * The argument must be in [0, 1], and the result is positive.
     */
    static double arcHav(double x) {
        return 2 * asin(sqrt(x));
    }

    private SphericalUtil() {}

    /**
     * Returns the heading from one LatLng to another LatLng. Headings are
     * expressed in degrees clockwise from North within the range [-180,180).
     * @return The heading in degrees clockwise from north.
     */
    public static double computeHeading(LatLng from, LatLng to) {
        // http://williams.best.vwh.net/avform.htm#Crs
        double fromLat = toRadians(from.latitude);
        double fromLng = toRadians(from.longitude);
        double toLat = toRadians(to.latitude);
        double toLng = toRadians(to.longitude);
        double dLng = toLng - fromLng;
        double heading = atan2(
                sin(dLng) * cos(toLat),
                cos(fromLat) * sin(toLat) - sin(fromLat) * cos(toLat) * cos(dLng));
        return wrap(toDegrees(heading), -180, 180);
    }

    /**
     * Returns the LatLng resulting from moving a distance from an origin
     * in the specified heading (expressed in degrees clockwise from north).
     * @param from     The LatLng from which to start.
     * @param distance The distance to travel.
     * @param heading  The heading in degrees clockwise from north.
     */
    public static LatLng computeOffset(LatLng from, double distance, double heading) {
        distance /= EARTH_RADIUS;
        heading = toRadians(heading);
        // http://williams.best.vwh.net/avform.htm#LL
        double fromLat = toRadians(from.latitude);
        double fromLng = toRadians(from.longitude);
        double cosDistance = cos(distance);
        double sinDistance = sin(distance);
        double sinFromLat = sin(fromLat);
        double cosFromLat = cos(fromLat);
        double sinLat = cosDistance * sinFromLat + sinDistance * cosFromLat * cos(heading);
        double dLng = atan2(
                sinDistance * cosFromLat * sin(heading),
                cosDistance - sinFromLat * sinLat);
        return new LatLng(toDegrees(asin(sinLat)), toDegrees(fromLng + dLng));
    }

    /**
     * Returns the location of origin when provided with a LatLng destination,
     * meters travelled and original heading. Headings are expressed in degrees
     * clockwise from North. This function returns null when no solution is
     * available.
     * @param to       The destination LatLng.
     * @param distance The distance travelled, in meters.
     * @param heading  The heading in degrees clockwise from north.
     */
    public static LatLng computeOffsetOrigin(LatLng to, double distance, double heading) {
        heading = toRadians(heading);
        distance /= EARTH_RADIUS;
        // http://lists.maptools.org/pipermail/proj/2008-October/003939.html
        double n1 = cos(distance);
        double n2 = sin(distance) * cos(heading);
        double n3 = sin(distance) * sin(heading);
        double n4 = sin(toRadians(to.latitude));
        // There are two solutions for b. b = n2 * n4 +/- sqrt(), one solution results
        // in the latitude outside the [-90, 90] range. We first try one solution and
        // back off to the other if we are outside that range.
        double n12 = n1 * n1;
        double discriminant = n2 * n2 * n12 + n12 * n12 - n12 * n4 * n4;
        if (discriminant < 0) {
            // No real solution which would make sense in LatLng-space.
            return null;
        }
        double b = n2 * n4 + sqrt(discriminant);
        b /= n1 * n1 + n2 * n2;
        double a = (n4 - n2 * b) / n1;
        double fromLatRadians = atan2(a, b);
        if (fromLatRadians < -PI / 2 || fromLatRadians > PI / 2) {
            b = n2 * n4 - sqrt(discriminant);
            b /= n1 * n1 + n2 * n2;
            fromLatRadians = atan2(a, b);
        }
        if (fromLatRadians < -PI / 2 || fromLatRadians > PI / 2) {
            // No solution which would make sense in LatLng-space.
            return null;
        }
        double fromLngRadians = toRadians(to.longitude) -
                atan2(n3, n1 * cos(fromLatRadians) - n2 * sin(fromLatRadians));
        return new LatLng(toDegrees(fromLatRadians), toDegrees(fromLngRadians));
    }

    /**
     * Returns the LatLng which lies the given fraction of the way between the
     * origin LatLng and the destination LatLng.
     * @param from     The LatLng from which to start.
     * @param to       The LatLng toward which to travel.
     * @param fraction A fraction of the distance to travel.
     * @return The interpolated LatLng.
     */
    public static LatLng interpolate(LatLng from, LatLng to, double fraction) {
        // http://en.wikipedia.org/wiki/Slerp
        double fromLat = toRadians(from.latitude);
        double fromLng = toRadians(from.longitude);
        double toLat = toRadians(to.latitude);
        double toLng = toRadians(to.longitude);
        double cosFromLat = cos(fromLat);
        double cosToLat = cos(toLat);

        // Computes Spherical interpolation coefficients.
        double angle = computeAngleBetween(from, to);
        double sinAngle = sin(angle);
        if (sinAngle < 1E-6) {
            return from;
        }
        double a = sin((1 - fraction) * angle) / sinAngle;
        double b = sin(fraction * angle) / sinAngle;

        // Converts from polar to vector and interpolate.
        double x = a * cosFromLat * cos(fromLng) + b * cosToLat * cos(toLng);
        double y = a * cosFromLat * sin(fromLng) + b * cosToLat * sin(toLng);
        double z = a * sin(fromLat) + b * sin(toLat);

        // Converts interpolated vector back to polar.
        double lat = atan2(z, sqrt(x * x + y * y));
        double lng = atan2(y, x);
        return new LatLng(toDegrees(lat), toDegrees(lng));
    }

    /**
     * Returns distance on the unit sphere; the arguments are in radians.
     */
    private static double distanceRadians(double lat1, double lng1, double lat2, double lng2) {
        return arcHav(havDistance(lat1, lat2, lng1 - lng2));
    }

    /**
     * Returns the angle between two LatLngs, in radians. This is the same as the distance
     * on the unit sphere.
     */
    static double computeAngleBetween(LatLng from, LatLng to) {
        return distanceRadians(toRadians(from.latitude), toRadians(from.longitude),
                               toRadians(to.latitude), toRadians(to.longitude));
    }

    /**
     * Returns the distance between two LatLngs, in meters.
     */
    public static double computeDistanceBetween(LatLng from, LatLng to) {
        return computeAngleBetween(from, to) * EARTH_RADIUS;
    }

    /**
     * Returns the length of the given path, in meters, on Earth.
     */
    public static double computeLength(List<LatLng> path) {
        if (path.size() < 2) {
            return 0;
        }
        double length = 0;
        LatLng prev = path.get(0);
        double prevLat = toRadians(prev.latitude);
        double prevLng = toRadians(prev.longitude);
        for (LatLng point : path) {
            double lat = toRadians(point.latitude);
            double lng = toRadians(point.longitude);
            length += distanceRadians(prevLat, prevLng, lat, lng);
            prevLat = lat;
            prevLng = lng;
        }
        return length * EARTH_RADIUS;
    }

    /**
     * Returns the area of a closed path on Earth.
     * @param path A closed path.
     * @return The path's area in square meters.
     */
    public static double computeArea(List<LatLng> path) {
        return abs(computeSignedArea(path));
    }

    /**
     * Returns the signed area of a closed path on Earth. The sign of the area may be used to
     * determine the orientation of the path.
     * "inside" is the surface that does not contain the South Pole.
     * @param path A closed path.
     * @return The loop's area in square meters.
     */
    public static double computeSignedArea(List<LatLng> path) {
        return computeSignedArea(path, EARTH_RADIUS);
    }

    /**
     * Returns the signed area of a closed path on a sphere of given radius.
     * The computed area uses the same units as the radius squared.
     * Used by SphericalUtilTest.
     */
    static double computeSignedArea(List<LatLng> path, double radius) {
        int size = path.size();
        if (size < 3) { return 0; }
        double total = 0;
        LatLng prev = path.get(size - 1);
        double prevTanLat = tan((PI / 2 - toRadians(prev.latitude)) / 2);
        double prevLng = toRadians(prev.longitude);
        // For each edge, accumulate the signed area of the triangle formed by the North Pole
        // and that edge ("polar triangle").
        for (LatLng point : path) {
            double tanLat = tan((PI / 2 - toRadians(point.latitude)) / 2);
            double lng = toRadians(point.longitude);
            total += polarTriangleArea(tanLat, lng, prevTanLat, prevLng);
            prevTanLat = tanLat;
            prevLng = lng;
        }
        return total * (radius * radius);
    }

    /**
     * Returns the signed area of a triangle which has North Pole as a vertex.
     * Formula derived from "Area of a spherical triangle given two edges and the included angle"
     * as per "Spherical Trigonometry" by Todhunter, page 71, section 103, point 2.
     * See http://books.google.com/books?id=3uBHAAAAIAAJ&pg=PA71
     * The arguments named "tan" are tan((pi/2 - latitude)/2).
     */
    private static double polarTriangleArea(double tan1, double lng1, double tan2, double lng2) {
        double deltaLng = lng1 - lng2;
        double t = tan1 * tan2;
        return 2 * atan2(t * sin(deltaLng), 1 + t * cos(deltaLng));
    }

    /**
     * Wraps the given value into the inclusive-exclusive interval between min and max.
     * @param n   The value to wrap.
     * @param min The minimum.
     * @param max The maximum.
     */
    static double wrap(double n, double min, double max) {
        return (n >= min && n < max) ? n : (mod(n - min, max - min) + min);
    }

    /**
     * Returns the non-negative remainder of x / m.
     * @param x The operand.
     * @param m The modulus.
     */
    static double mod(double x, double m) {
        return ((x % m) + m) % m;
    }
}

Leave a Comment