/* ------------------------------------------------------------------------------
*
* # Showing coordinates
*
* Specific JS code additions for maps_google_basic.html page
*
* Version: 1.0
* Latest update: Aug 1, 2015
*
* ---------------------------------------------------------------------------- */
$(function() {
// Variables
var map;
var TILE_SIZE = 256;
var chicago = new google.maps.LatLng(41.850033,-87.6500523);
// Minimum and maximum values
function bound(value, opt_min, opt_max) {
if (opt_min != null) value = Math.max(value, opt_min);
if (opt_max != null) value = Math.min(value, opt_max);
return value;
}
// Degrees to radians
function degreesToRadians(deg) {
return deg * (Math.PI / 180);
}
// Radians to degrees
function radiansToDegrees(rad) {
return rad / (Math.PI / 180);
}
// Constructor
function MercatorProjection() {
this.pixelOrigin_ = new google.maps.Point(TILE_SIZE / 2, TILE_SIZE / 2);
this.pixelsPerLonDegree_ = TILE_SIZE / 360;
this.pixelsPerLonRadian_ = TILE_SIZE / (2 * Math.PI);
}
// From latitude to longitude
MercatorProjection.prototype.fromLatLngToPoint = function(latLng, opt_point) {
var me = this;
var point = opt_point || new google.maps.Point(0, 0);
var origin = me.pixelOrigin_;
point.x = origin.x + latLng.lng() * me.pixelsPerLonDegree_;
// Truncating to 0.9999 effectively limits latitude to 89.189. This is
// about a third of a tile past the edge of the world tile.
var siny = bound(Math.sin(degreesToRadians(latLng.lat())), -0.9999, 0.9999);
point.y = origin.y + 0.5 * Math.log((1 + siny) / (1 - siny)) * -me.pixelsPerLonRadian_;
return point;
};
// From longitude to latitude
MercatorProjection.prototype.fromPointToLatLng = function(point) {
var me = this;
var origin = me.pixelOrigin_;
var lng = (point.x - origin.x) / me.pixelsPerLonDegree_;
var latRadians = (point.y - origin.y) / -me.pixelsPerLonRadian_;
var lat = radiansToDegrees(2 * Math.atan(Math.exp(latRadians)) - Math.PI / 2);
return new google.maps.LatLng(lat, lng);
};
// Create content
function createInfoWindowContent() {
var numTiles = 1 << map.getZoom();
var projection = new MercatorProjection();
var worldCoordinate = projection.fromLatLngToPoint(chicago);
var pixelCoordinate = new google.maps.Point(worldCoordinate.x * numTiles, worldCoordinate.y * numTiles);
var tileCoordinate = new google.maps.Point(
Math.floor(pixelCoordinate.x / TILE_SIZE),
Math.floor(pixelCoordinate.y / TILE_SIZE));
return [
'Chicago, IL',
'LatLng: ' + chicago.lat() + ' , ' + chicago.lng(),
'World Coordinate: ' + worldCoordinate.x + ' , ' + worldCoordinate.y,
'Pixel Coordinate: ' + Math.floor(pixelCoordinate.x) + ' , ' + Math.floor(pixelCoordinate.y),
'Tile Coordinate: ' + tileCoordinate.x + ' , ' + tileCoordinate.y + ' at Zoom Level: ' + map.getZoom()
].join('
');
}
// Initialize
function initialize() {
// Options
var mapOptions = {
zoom: 10,
center: chicago
};
// Apply options
map = new google.maps.Map($('.map-coordinates')[0], mapOptions);
// Info window
var coordInfoWindow = new google.maps.InfoWindow();
coordInfoWindow.setContent(createInfoWindowContent());
coordInfoWindow.setPosition(chicago);
coordInfoWindow.open(map);
// Add "Change" event
google.maps.event.addListener(map, 'zoom_changed', function() {
coordInfoWindow.setContent(createInfoWindowContent());
coordInfoWindow.open(map);
});
}
// Load map
google.maps.event.addDomListener(window, 'load', initialize);
});