如何在google maps api中找出该区域

Question

我正在做地图应用程序，我需要找出地图的区域，最小纬度，最大纬度，最小经度，最大经度。我这样做了，但不确定这是不是正确的方法，我在这里感到困惑，

谷歌地图添加事件侦听器缩放基于我需要获取地图的区域和 MIN,MAX（纬度，经度），使用此值我可以在 DB 中找到正确的多边形并显示基于该的多边形的正确结果区域缩放级别，基于 MIN,MAX(latitude,longitude)。

任何人都可以建议这是正确的方法，否则我需要更改我的代码

    <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.3/jquery.min.js"></script>
    <script type="text/javascript" src="http://maps.google.com/maps/api/js?libraries=geometry,places&sensor=true"></script>
    <script>
    function initialize() {
       alert("ok");
        var mapOptions = {
            zoom: 14,
            center: new google.maps.LatLng(24.4799425,73.0934957),
            mapTypeId: google.maps.MapTypeId.ROADMAP
        };

        var map = new google.maps.Map(document.getElementById('map-canvas'),  mapOptions);
        var arr = new Array();
        var polygons = [];
        var bounds = new google.maps.LatLngBounds();
        var coordinates = [];
        var marker = new google.maps.Marker;
        var getBounds;

        // downloadUrl("subdivision-coordinates.php", function(data) {
            //var xmlString = $('#xml_values').val();
            var xmlString ="<subdivisions><subdivision name='Madivala'><coord lat='12.920496072962534' lng='77.6198673248291' id='6' /><coord lat='12.92409332232521' lng='77.62896537780762' id='6' /><coord lat='12.927439554274295' lng='77.6209831237793' id='6' /><coord lat='12.923340413955895' lng='77.61634826660156' id='6' /><coord lat='12.92066338803538' lng='77.61960983276367' id='6' /></subdivision><subdivision name='Sarjapur'><coord lat='12.91706608927013' lng='77.62372970581055' id='7' /><coord lat='12.9158948645401' lng='77.6389217376709' id='7' /><coord lat='12.919659495917085' lng='77.64299869537354' id='7' /><coord lat='12.92409332232521' lng='77.64793395996094' id='7' /><coord lat='12.92480440036714' lng='77.63424396514893' id='7' /><coord lat='12.920998017844783' lng='77.62089729309082' id='7' /></subdivision><subdivision name='Domulur'><coord lat='12.967758119178917' lng='77.63282775878906' id='8' /><coord lat='12.962237705403682' lng='77.65179634094238' id='8' /><coord lat='12.950025446093244' lng='77.64226913452148' id='8' /><coord lat='12.963826927981351' lng='77.6308536529541' id='8' /><coord lat='12.967507193936736' lng='77.63299942016602' id='8' /></subdivision><subdivision name='Indira Nagar'><coord lat='12.982227713276773' lng='77.63505935668945' id='9' /><coord lat='12.985154985380868' lng='77.64518737792969' id='9' /><coord lat='12.965834352522322' lng='77.64904975891113' id='9' /><coord lat='12.965834352522322' lng='77.63694763183594' id='9' /><coord lat='12.982060439543622' lng='77.63497352600098' id='9' /></subdivision><subdivision name='Mariyapan Palya'><coord lat='12.97846402705198' lng='77.54322052001953' id='10' /><coord lat='12.9792167688559' lng='77.56536483764648' id='10' /><coord lat='12.95671716919877' lng='77.56914138793945' id='10' /><coord lat='12.956298941771568' lng='77.54373550415039' id='10' /></subdivision></subdivisions>";
            var xml = xmlParse(xmlString);
            var subdivision = xml.getElementsByTagName("subdivision");
            for (var i = 0; i < subdivision.length; i++) {
                arr = [];
                var coordinates = xml.documentElement.getElementsByTagName("subdivision")[i].getElementsByTagName("coord");
                //console.log("coordinates="+xml.documentElement.getElementsByTagName("subdivision")[i].getElementsByTagName("coord"));


                for (var j=0; j < coordinates.length; j++) {
                  arr.push(new google.maps.LatLng(
                        parseFloat(coordinates[j].getAttribute("lat")),
                        parseFloat(coordinates[j].getAttribute("lng"))
                  ));

                  var idd=coordinates[j].getAttribute("id");  
                  bounds.extend(arr[arr.length-1]);

                }

                polygons.push(new google.maps.Polygon({
                    id: idd,
                    paths: arr,
                    strokeColor: '#BA55D3',
                    strokeOpacity: 0.8,
                    strokeWeight: 2,
                    fillColor: '#DA70D6',
                    fillOpacity: 0.35
                }));
                polygons[polygons.length-1].setMap(map);

                polygons[polygons.length-1].addListener('click', function (event) {
                    //alert(this.id);
                      var service_name=$('input[name="map_service"]:checked').val();
                      $('#add_to_qh').val(this.id);
                      $('#loc_edit_page').attr('href',"locality_service_edit.php?geoId="+this.id+"&service="+service_name);
                      $("#myModal").modal();
                });
                polygons[polygons.length-1].addListener('rightclick', function (event) {

                    console.log("Need to delete the clicked polygon");
                });


            }

      map.fitBounds(bounds);

              google.maps.event.addListener(map, 'idle', function() {
                zoomLevel = map.getZoom();
                  center=map.getCenter();

                  var bounds1 = map.getBounds();

                  var min_lat = bounds1.getSouthWest().lat();
                  var min_lng = bounds1.getSouthWest().lng();

                  var max_lat = bounds1.getNorthEast().lat();
                  var max_lng = bounds1.getNorthEast().lng();

                  var nw = new google.maps.LatLng(min_lat, max_lng);
                  var se = new google.maps.LatLng(max_lat, min_lng);

                  var area22=google.maps.geometry.spherical.computeArea([bounds1.getNorthEast(),se, bounds1.getSouthWest(), nw]);
                  //Area chage meter2 to meter 
                  area22 = area22/1000000;


                  var min_area = area22-((area22*20)/100);
                  var max_area = area22+((area22*20)/100);

                  $('#area').val(area22);

                  $('#min_area').val(min_area);
                  $('#max_area').val(max_area);

                  $('#min_lat').val(min_lat);
                  $('#max_lat').val(max_lat);
                  $('#min_lng').val(min_lng);
                  $('#max_lng').val(max_lng);

                  //console.log("Zoommmmmm   my area="+area+" Min Area="+min_area+ " Max Area="+max_area);
               });


    }

    function xmlParse(str) {
      if (typeof ActiveXObject != 'undefined' && typeof GetObject != 'undefined') {
        var doc = new ActiveXObject('Microsoft.XMLDOM');
        doc.loadXML(str);
        return doc;
      }

      if (typeof DOMParser != 'undefined') {
        return (new DOMParser()).parseFromString(str, 'text/xml');
      }

      return createElement('div', null);
    }

    $(function(){
    initialize();
    });

    </script>
    <div id="map-canvas" style="height:620px;" ></div>    
    <input type="text" id="hidden" name="min_area" /> 
    <input type="text" id="hidden" name="max_area" /> 
    Area : <input type="text" id="area" name="area" /> 
    Min Lat : <input type="text" id="min_lat" name="min_lat" /> 
    Max Lat : <input type="text" id="max_lat" name="max_lat" /> 
    Min Lng : <input type="text" id="min_lng" name="min_lng" /> 
    Max Lng : <input type="text" id="max_lng" name="max_lng" /> 

Answer 1

您可以很容易地找到区域。 在计算面积之前，请确保地图已经加载。

您需要做的就是获取地图边界，然后提取（并正确使用）角落的坐标。

var bounds = map.getBounds();
var ne = bounds.getNorthEast(); // LatLng of the north-east corner
var sw = bounds.getSouthWest(); // LatLng of the south-west corder

您可以从上面的两个角落获得西北角和东南角：

var nw = new google.maps.LatLng(ne.lat(), sw.lng());
var se = new google.maps.LatLng(sw.lat(), ne.lng());

现在定义一个函数为 getDistanceInMeters

function getDistanceInMeters(location1, location2) {
    var lat1 = location1.lat();
    var lon1 = location1.lng();

    var lat2 = location2.lat();
    var lon2 = location2.lng();

    var R = 6371; // Radius of the earth in km
    var dLat = deg2rad(lat2 - lat1);
    var dLon = deg2rad(lon2 - lon1);
    var a =
      Math.sin(dLat / 2) * Math.sin(dLat / 2) +
      Math.cos(deg2rad(lat1)) * Math.cos(deg2rad(lat2)) *
      Math.sin(dLon / 2) * Math.sin(dLon / 2);
    var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
    var d = R * c; // Distance in km
    return (d * 1000);

    function deg2rad(deg) {
        return deg * (Math.PI / 180);
    }
}

利用这个函数计算地图的长宽，然后求面积。

var length = getDistanceInMeters(sw, nw);
var breadth = getDistanceInMeters(sw, se);

现在区域，

var area = length * breadth; // in square meters

---

引用自：get boundaries longitude and latitude from current zoom google maps

Answer 2

一种更简单的方法可能是使用内置的谷歌地图功能，即

var bounds = map.getBounds();
var ne = bounds.getNorthEast(); 
var sw = bounds.getSouthWest();
var nw = new google.maps.LatLng(ne.lat(), sw.lng());
var se = new google.maps.LatLng(sw.lat(), ne.lng());

var latLngList: google.maps.LatLng[] = [ne, nw, sw, se];
console.log("Area is", google.maps.geometry.spherical.computeArea(latLngList));

请注意，您必须将“几何”库加载为 googlemaps 的一部分，即

<script src="https://maps.googleapis.com/maps/api/js?key=YOUR_API_KEY&libraries=geometry">