WMS on Google Map, USGS topo example

Getting WMS data on Google Maps

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Querying your map for lat/lng points

In this map, I added a function that send the lat/lng for the point you clicked to a php program that calculates the info needed for a WMS GetFeatureInfo query. A WMS GetFeatureInfo query needs the bbox of the tile you are querying and the pixel distance to the point in that bbox. You can get the code for this php script here.

When you click on this map it is querying the shapefile that contains all USFS roadless areas. The window shows the bbox and pixel info that is sent to the WMS server and the information returned by the query. You'll notice that the query doesn't return anything if you don't click on the green roadless areas.

Here is the code for the map on this page:

<script type="text/javascript"> // best to declare your map variable outside of the function so that you can access it from other functions var map; function initialize() { if (GBrowserIsCompatible()) { // set up the map map = new GMap2(document.getElementById("map_canvas")); // set up your wms layer var tile_roadless; tile_roadless= new GTileLayer(new GCopyrightCollection(""),1,17); // these are the layers from your mapserver map file tile_roadless.myLayers = 'ira_fill2,ira_line,wild_hatch'; tile_roadless.myMercZoomLevel=5; tile_roadless.myFormat='image/gif'; // this is the address of your mapserver map tile_roadless.myBaseURL= 'http://thewildwoodstudios.com/cgi-bin/mapserv?map=../roadlessland/maps/ira.map&'; // this is the function performed by John Deck's script tile_roadless.getTileUrl=CustomGetTileUrl; // this specifies the opacity of your layer tile_roadless.getOpacity = function() {return 1.0;} map.addControl(new GLargeMapControl()); map.addControl(new GMapTypeControl()); // set the location of the map map.setCenter(new GLatLng(35.846760876811366, -106.03317260742188), 10); // add wms layer with GTileLayerOverlay var MapserverLayer = new GTileLayerOverlay(tile_roadless); map.addOverlay(MapserverLayer); // add a function that listens for a click on the map and records the lat/lng from that point // this function calls another function that I call get_point() click_listen = GEvent.addListener(map, 'click', function(overlay,latlng) { get_place(latlng); }); } } function get_place(latlng) { var zm = map.getZoom(); if(zm < 8) { zm=8; } var url = 'lat='+latlng.lat()+'&lng='+latlng.lng()+'&z='+zm; var urlstr = 'get_point.php?q=1&' + url; GDownloadUrl(urlstr,function(doc) { var result = doc; var info = '<div style="width:350px;"><small>'; info += 'The lat / lng you clicked:<br />'; info += latlng.lat() + ', ' + latlng.lng() + '<p />'; info += 'The bbox and xy data required for a wms query:<br />'; info += doc; info += '</small></div>'; map.openInfoWindow(latlng, info); }); } </script>