map.service.js

(function () {
  'use strict';
  angular
    .module('com.module.core')
    .service('MapService', function () {

      var rad = function(x) { return x*Math.PI/180;}

      var distHaversine = function(latLngBounds) {
        var R = 6371; // earth's mean radius in km
        var bounds = latLngBounds.toJSON();
        var dLat  = rad(bounds.east - bounds.west);
        var dLong = rad(bounds.south - bounds.north);

        var a = Math.sin(dLat/2) * Math.sin(dLat/2) +
                Math.cos(rad(bounds.east)) * Math.cos(rad(bounds.west)) * Math.sin(dLong/2) * Math.sin(dLong/2);
        var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a));
        var d = R * c;
        return d.toFixed(3);
      }

      var calculateZoomFromHaversineDist = function(dist) {
        var zoom = 4;
        if(dist < 1.25) {
          zoom = 15;
        } else if(dist < 2.5) {
          zoom = 14;
        } else if(dist < 5) {
          zoom = 13;
        } else if(dist < 10) {
          zoom = 12;
        } else if(dist < 20) {
          zoom = 11;
        } else if(dist < 40) {
          zoom = 10;
        } else if(dist < 80) {
          zoom = 9;
        } else if(dist < 160) {
          zoom = 8;
        } else if(dist < 320) {
          zoom = 7;
        } else if(dist < 640) {
          zoom = 6;
        } else if(dist < 1180) {
          zoom = 6;
        } else if(dist < 2360) {
          zoom = 5;
        }
        return zoom;
      }

      this.fitToLatLngBounds = function(latLngBounds) {
        this.map.panTo(latLngBounds.getCenter());
        this.map.fitBounds(latLngBounds);
        this.zoomFromLatLngBounds(latLngBounds);
      }

      this.zoomFromLatLngBounds = function(latLngBounds) {
        var dist = distHaversine(latLngBounds);
        console.log("Harvesine dist from bounds", dist);
        var zoom = calculateZoomFromHaversineDist(dist);
        console.log("Resulting zoom level from harvesine", zoom);
        this.map.setZoom(zoom);
      };

      this.setMap = function(mapInstance) {
        this.map = mapInstance;
      };
    });
})();