Midpoint on Google Maps

Question

I was wondering if anyone knows how to use google maps api to find the middle of the route between two places. I do not want a geographical center, but rather a midpoint over a long distance. I am new to both Javascript and google maps api, so if you could add a demo or code with your answer, that would be very helpful. The end result will output the latitude and longitude and will represent something like what this website has: http://www.geomidpoint.com/meet/ . Thank you for your help!

Answer 1

An example that calculates the middle of a route

Uses the v3 version of the epoly library of Mike Williams.

var directionDisplay; var directionsService = new google.maps.DirectionsService(); var map; var polyline = null; var infowindow = new google.maps.InfoWindow(); function createMarker(latlng, label, html) { var contentString = '<b>'+label+'</b><br>'+html; var marker = new google.maps.Marker({ position: latlng, map: map, title: label, zIndex: Math.round(latlng.lat()*-100000)<<5 }); marker.myname = label; google.maps.event.addListener(marker, 'click', function() { infowindow.setContent(contentString+"<br>"+marker.getPosition().toUrlValue(6)); infowindow.open(map,marker); }); return marker; } function initialize() { directionsDisplay = new google.maps.DirectionsRenderer({suppressMarkers:true}); var chicago = new google.maps.LatLng(41.850033, -87.6500523); var myOptions = { zoom: 6, mapTypeId: google.maps.MapTypeId.ROADMAP, center: chicago } map = new google.maps.Map(document.getElementById("map_canvas"), myOptions); polyline = new google.maps.Polyline({ path: [], strokeColor: '#FF0000', strokeWeight: 3 }); directionsDisplay.setMap(map); calcRoute(); } function calcRoute() { var start = document.getElementById("start").value; var end = document.getElementById("end").value; var travelMode = google.maps.DirectionsTravelMode.DRIVING var request = { origin: start, destination: end, travelMode: travelMode }; directionsService.route(request, function(response, status) { if (status == google.maps.DirectionsStatus.OK) { polyline.setPath([]); var bounds = new google.maps.LatLngBounds(); startLocation = new Object(); endLocation = new Object(); directionsDisplay.setDirections(response); var route = response.routes[0]; var summaryPanel = document.getElementById("directions_panel"); summaryPanel.innerHTML = ""; // For each route, display summary information. var path = response.routes[0].overview_path; var legs = response.routes[0].legs; for (i=0;i<legs.length;i++) { if (i == 0) { startLocation.latlng = legs[i].start_location; startLocation.address = legs[i].start_address; marker = createMarker(legs[i].start_location,"midpoint","","green"); } endLocation.latlng = legs[i].end_location; endLocation.address = legs[i].end_address; var steps = legs[i].steps; for (j=0;j<steps.length;j++) { var nextSegment = steps[j].path; for (k=0;k<nextSegment.length;k++) { polyline.getPath().push(nextSegment[k]); bounds.extend(nextSegment[k]); } } } polyline.setMap(map); computeTotalDistance(response); } else { alert("directions response "+status); } }); } var totalDist = 0; var totalTime = 0; function computeTotalDistance(result) { totalDist = 0; totalTime = 0; var myroute = result.routes[0]; for (i = 0; i < myroute.legs.length; i++) { totalDist += myroute.legs[i].distance.value; totalTime += myroute.legs[i].duration.value; } putMarkerOnRoute(50); totalDist = totalDist / 1000. document.getElementById("total").innerHTML = "total distance is: "+ totalDist + " km<br>total time is: " + (totalTime / 60).toFixed(2) + " minutes"; } function putMarkerOnRoute(percentage) { var distance = (percentage/100) * totalDist; var time = ((percentage/100) * totalTime/60).toFixed(2); if (!marker) { marker = createMarker(polyline.GetPointAtDistance(distance),"time: "+time,"marker"); } else { marker.setPosition(polyline.GetPointAtDistance(distance)); marker.setTitle("time:"+time); } }