问题
I have a Google Maps Circle drawn on v3 api. When the user has plotted there circle (or polygon if they choose), they can save the data to the server. If the user has picked a radial search, the Centre coordinates and the radius in feet is stored to the database. This means when the user reloads his search, it can pull through the circle again (like below).
I'm having 1 problem, however, which is when the user selects what search they would like to use. It loads the polygon fine, if they drew a polygon, and if it's a circle it pulls through the marker on the center. However what I need is a function in static maps to draw a circle.
回答1:
A bit late in the game, but nothing I found solved my issue (serverside php only, no javascript). I ended up getting there in the end and have detailed my method here: http://jomacinc.com/map-radius/ and the short version is below.
This PHP function will return an encoded polyline string of lat/lng points in a circle around the specified point, and at the specified radius. The function requires Gabriel Svennerberg’s PHP polyline encoding class available here (http://www.svennerberg.com/examples/polylines/PolylineEncoder.php.txt).
function GMapCircle($Lat,$Lng,$Rad,$Detail=8){
$R = 6371;
$pi = pi();
$Lat = ($Lat * $pi) / 180;
$Lng = ($Lng * $pi) / 180;
$d = $Rad / $R;
$points = array();
$i = 0;
for($i = 0; $i <= 360; $i+=$Detail):
$brng = $i * $pi / 180;
$pLat = asin(sin($Lat)*cos($d) + cos($Lat)*sin($d)*cos($brng));
$pLng = (($Lng + atan2(sin($brng)*sin($d)*cos($Lat), cos($d)-sin($Lat)*sin($pLat))) * 180) / $pi;
$pLat = ($pLat * 180) /$pi;
$points[] = array($pLat,$pLng);
endfor;
require_once('PolylineEncoder.php');
$PolyEnc = new PolylineEncoder($points);
$EncString = $PolyEnc->dpEncode();
return $EncString['Points'];
}
You can now the use the above function to create a static map.
/* set some options */
$MapLat = '-42.88188'; // latitude for map and circle center
$MapLng = '147.32427'; // longitude as above
$MapRadius = 100; // the radius of our circle (in Kilometres)
$MapFill = 'E85F0E'; // fill colour of our circle
$MapBorder = '91A93A'; // border colour of our circle
$MapWidth = 640; // map image width (max 640px)
$MapHeight = 480; // map image height (max 640px)
/* create our encoded polyline string */
$EncString = GMapCircle($MapLat,$MapLng, $MapRadius);
/* put together the static map URL */
$MapAPI = 'http://maps.google.com.au/maps/api/staticmap?';
$MapURL = $MapAPI.'center='.$MapLat.','.$MapLng.'&size='.$MapWidth.'x'.$MapHeight.'&maptype=roadmap&path=fillcolor:0x'.$MapFill.'33%7Ccolor:0x'.$MapBorder.'00%7Cenc:'.$EncString.'&sensor=false';
/* output an image tag with our map as the source */
echo '<img src="'.$MapURL.'" />'
回答2:
function GMapCircle(lat,lng,rad,detail=8){
var uri = 'https://maps.googleapis.com/maps/api/staticmap?';
var staticMapSrc = 'center=' + lat + ',' + lng;
staticMapSrc += '&size=100x100';
staticMapSrc += '&path=color:0xff0000ff:weight:1';
var r = 6371;
var pi = Math.PI;
var _lat = (lat * pi) / 180;
var _lng = (lng * pi) / 180;
var d = (rad/1000) / r;
var i = 0;
for(i = 0; i <= 360; i+=detail) {
var brng = i * pi / 180;
var pLat = Math.asin(Math.sin(_lat) * Math.cos(d) + Math.cos(_lat) * Math.sin(d) * Math.cos(brng));
var pLng = ((_lng + Math.atan2(Math.sin(brng) * Math.sin(d) * Math.cos(_lat), Math.cos(d) - Math.sin(_lat) * Math.sin(pLat))) * 180) / pi;
pLat = (pLat * 180) / pi;
staticMapSrc += "|" + pLat + "," + pLng;
}
return uri + encodeURI(staticMapSrc);}
Javascript version
回答3:
Based on the answer from Jomac, Here is a Java/Android version of the same code.
It uses the PolyUtil class from Google Maps Android API Utility Library to encode the path.
import android.location.Location;
import com.google.android.gms.maps.model.LatLng;
import com.google.maps.android.PolyUtil;
import java.util.ArrayList;
public class GoogleStaticMapsAPIServices
{
private static final double EARTH_RADIUS_KM = 6371;
private static String GOOGLE_STATIC_MAPS_API_KEY = "XXXXXXXXXXXXX";
public static String getStaticMapURL(Location location, int radiusMeters)
{
String pathString = "";
if (radiusMeters > 0)
{
// Add radius path
ArrayList<LatLng> circlePoints = getCircleAsPolyline(location, radiusMeters);
if (circlePoints.size() > 0)
{
String encodedPathLocations = PolyUtil.encode(circlePoints);
pathString = "&path=color:0x0000ffff%7Cweight:1%7Cfillcolor:0x0000ff80%7Cenc:" + encodedPathLocations;
}
}
String staticMapURL = "https://maps.googleapis.com/maps/api/staticmap?size=640x320&markers=color:red%7C" +
location.getLatitude() + "," + location.getLongitude() +
pathString +
"&key=" + GOOGLE_STATIC_MAPS_API_KEY;
return staticMapURL;
}
private static ArrayList<LatLng> getCircleAsPolyline(Location center, int radiusMeters)
{
ArrayList<LatLng> path = new ArrayList<>();
double latitudeRadians = center.getLatitude() * Math.PI / 180.0;
double longitudeRadians = center.getLongitude() * Math.PI / 180.0;
double radiusRadians = radiusMeters / 1000.0 / EARTH_RADIUS_KM;
double calcLatPrefix = Math.sin(latitudeRadians) * Math.cos(radiusRadians);
double calcLatSuffix = Math.cos(latitudeRadians) * Math.sin(radiusRadians);
for (int angle = 0; angle < 361; angle += 10)
{
double angleRadians = angle * Math.PI / 180.0;
double latitude = Math.asin(calcLatPrefix + calcLatSuffix * Math.cos(angleRadians));
double longitude = ((longitudeRadians + Math.atan2(Math.sin(angleRadians) * Math.sin(radiusRadians) * Math.cos(latitudeRadians), Math.cos(radiusRadians) - Math.sin(latitudeRadians) * Math.sin(latitude))) * 180) / Math.PI;
latitude = latitude * 180.0 / Math.PI;
path.add(new LatLng(latitude, longitude));
}
return path;
}
}
回答4:
I think it is not possible to draw a circle on a static Google map. You would need to approximate the circle by a polyline (best in encoded format). This has already been mentioned in Stackoverflow and it is demonstrated e.g. by Free Map Tools.
回答5:
Sharing my C# version
private string GMapCircle(double lat, double lng, double rad, int detail = 8)
{
const string uri = "https://maps.googleapis.com/maps/api/staticmap?";
var staticMapSrc = "center=" + lat + "," + lng;
staticMapSrc += "&zoom=16";
staticMapSrc += "&maptype=satellite";
staticMapSrc += "&key=[YOURKEYHERE]";
staticMapSrc += "&size=640x426";
staticMapSrc += "&path=color:0xff0000ff:weight:1";
const int r = 6371;
const double pi = Math.PI;
var latAux = (lat * pi) / 180;
var longAux = (lng * pi) / 180;
var d = (rad / 1000) / r;
var i = 0;
if (rad > 0)
{
for (i = 0; i <= 360; i += detail)
{
var brng = i * pi / 180;
var pLat = Math.Asin(Math.Sin(latAux) * Math.Cos(d) + Math.Cos(latAux) * Math.Sin(d) * Math.Cos(brng));
var pLng = ((longAux + Math.Atan2(Math.Sin(brng) * Math.Sin(d) * Math.Cos(latAux), Math.Cos(d) - Math.Sin(latAux) * Math.Sin(pLat))) * 180) / pi;
pLat = (pLat * 180) / pi;
staticMapSrc += "|" + pLat + "," + pLng;
}
}
else
{
//TODO - Add marker
}
return uri + staticMapSrc;
}
来源：https://stackoverflow.com/questions/7316963/drawing-a-circle-google-static-maps