绘制一圈Google静态地图 [英] Drawing a circle Google Static Maps

问题描述

我在v3 api上绘制了Google地图圈。当用户在那里绘制圆圈（或者如果他们选择了多边形），他们可以将数据保存到服务器。如果用户选择了径向搜索，则将中心坐标和以英尺为单位的半径存储到数据库中。这意味着当用户重新加载搜索时，它可以再次通过该圆圈（如下所示）。

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).

我有1个问题，但是，当用户选择他们想要的搜索时使用。如果多边形绘制了多边形，它会加载多边形，如果它是一个圆形，则会穿过中心的标记。然而，我需要的是静态地图中的一个函数来绘制一个圆。

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.

推荐答案

在游戏中有点迟，但没有发现解决了我的问题（serverside php only，no javascript）。
我最后到达那里并详细说明了我的方法： http://jomacinc.com/map-radius/ 和短版本在下面。

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.

这个PHP函数将在指定点周围的圆圈内返回经纬度为lat / lng的编码多段线，并且在指定的半径。该功能需要Gabriel Svennerberg的PHP折线编码类（ http://www.svennerberg.com/examples/ Pollinines / PolylineEncoder.php.txt ）。

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'];
}

现在可以使用上述函数创建静态地图。 p>

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.'" />'

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