使用Google API directions我可以获取从一个地方到另一个地方的所有信息，我也可以完成所有步骤。
但我不知道在给定时间后是否有办法检索/计算位置（Lat / Lng）。假设，为了简化，我的速度是恒定的，我可以回答这个问题：我将在X分钟的哪个位置？
注意
我知道Distance travelled = Time * Speed但是通过这种方式，我知道我走了多少公里。我想知道的是一段时间后的（Lat / Lng）。
答案 0 :(得分：0)
working example使用从epoly.js third party library from Mike Williams移植到v3的GetPointAtDistance
var directionDisplay;
var directionsService = new google.maps.DirectionsService();
var map;
var polyline = null;
function createMarker(latlng, label, html) {
// alert("createMarker("+latlng+","+label+","+html+","+color+")");
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;
// gmarkers.push(marker);
google.maps.event.addListener(marker, 'click', function() {
infowindow.setContent(contentString);
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 = google.maps.Marker({map:map,position: startLocation.latlng});
marker = createMarker(legs[i].start_location,"start",legs[i].start_address,"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;
}
totalDist = totalDist / 1000.
document.getElementById("total").innerHTML = "total distance is: "+ totalDist + " km<br>total time is: " + (totalTime / 60).toFixed(2) + " minutes";
document.getElementById("totalTime").value = (totalTime/60.).toFixed(2);
}
function putMarkerOnRoute(time) {
var distance = (time*60/totalTime) * totalDist*1000;
// alert("Time:"+time+" totalTime:"+totalTime+" totalDist:"+totalDist+" dist:"+distance);
if (!marker) {
marker = createMarker(polyline.GetPointAtDistance(distance),"time: "+time,"marker");
} else {
marker.setPosition(polyline.GetPointAtDistance(distance));
marker.setTitle("time:"+time);
}
}
v3_epoly.js
/*********************************************************************\
* *
* epolys.js by Mike Williams *
* updated to API v3 by Larry Ross *
* *
* A Google Maps API Extension *
* *
* Adds various Methods to google.maps.Polygon and google.maps.Polyline *
* *
* .GetPointAtDistance() returns a GLatLng at the specified distance *
* along the path. *
* The distance is specified in metres *
* Reurns null if the path is shorter than that *
* *
* .GetPointsAtDistance() returns an array of GLatLngs at the *
* specified interval along the path. *
* The distance is specified in metres *
* *
***********************************************************************
* *
* This Javascript is provided by Mike Williams *
* Blackpool Community Church Javascript Team *
* http://www.blackpoolchurch.org/ *
* http://econym.org.uk/gmap/ *
* *
* This work is licenced under a Creative Commons Licence *
* http://creativecommons.org/licenses/by/2.0/uk/ *
* *
***********************************************************************
* *
* Version 1.1 6-Jun-2007 *
* Version 1.2 1-Jul-2007 - fix: Bounds was omitting vertex zero *
* add: Bearing *
* Version 1.3 28-Nov-2008 add: GetPointsAtDistance() *
* Version 1.4 12-Jan-2009 fix: GetPointsAtDistance() *
* Version 3.0 11-Aug-2010 update to v3 *
* *
\*********************************************************************/
// === first support methods that don't (yet) exist in v3
google.maps.LatLng.prototype.distanceFrom = function(newLatLng) {
var EarthRadiusMeters = 6378137.0; // meters
var lat1 = this.lat();
var lon1 = this.lng();
var lat2 = newLatLng.lat();
var lon2 = newLatLng.lng();
var dLat = (lat2-lat1) * Math.PI / 180;
var dLon = (lon2-lon1) * Math.PI / 180;
var a = Math.sin(dLat/2) * Math.sin(dLat/2) +
Math.cos(lat1 * Math.PI / 180 ) * Math.cos(lat2 * Math.PI / 180 ) *
Math.sin(dLon/2) * Math.sin(dLon/2);
var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a));
var d = EarthRadiusMeters * c;
return d;
}
google.maps.LatLng.prototype.latRadians = function() {
return this.lat() * Math.PI/180;
}
google.maps.LatLng.prototype.lngRadians = function() {
return this.lng() * Math.PI/180;
}
// === A method which returns the length of a path in metres ===
google.maps.Polygon.prototype.Distance = function() {
var dist = 0;
for (var i=1; i < this.getPath().getLength(); i++) {
dist += this.getPath().getAt(i).distanceFrom(this.getPath().getAt(i-1));
}
return dist;
}
// === A method which returns a GLatLng of a point a given distance along the path ===
// === Returns null if the path is shorter than the specified distance ===
google.maps.Polygon.prototype.GetPointAtDistance = function(metres) {
// some awkward special cases
if (metres == 0) return this.getPath().getAt(0);
if (metres < 0) return null;
if (this.getPath().getLength() < 2) return null;
var dist=0;
var olddist=0;
for (var i=1; (i < this.getPath().getLength() && dist < metres); i++) {
olddist = dist;
dist += this.getPath().getAt(i).distanceFrom(this.getPath().getAt(i-1));
}
if (dist < metres) {
return null;
}
var p1= this.getPath().getAt(i-2);
var p2= this.getPath().getAt(i-1);
var m = (metres-olddist)/(dist-olddist);
return new google.maps.LatLng( p1.lat() + (p2.lat()-p1.lat())*m, p1.lng() + (p2.lng()-p1.lng())*m);
}
// === A method which returns an array of GLatLngs of points a given interval along the path ===
google.maps.Polygon.prototype.GetPointsAtDistance = function(metres) {
var next = metres;
var points = [];
// some awkward special cases
if (metres <= 0) return points;
var dist=0;
var olddist=0;
for (var i=1; (i < this.getPath().getLength()); i++) {
olddist = dist;
dist += this.getPath().getAt(i).distanceFrom(this.getPath().getAt(i-1));
while (dist > next) {
var p1= this.getPath().getAt(i-1);
var p2= this.getPath().getAt(i);
var m = (next-olddist)/(dist-olddist);
points.push(new google.maps.LatLng( p1.lat() + (p2.lat()-p1.lat())*m, p1.lng() + (p2.lng()-p1.lng())*m));
next += metres;
}
}
return points;
}
// === Copy all the above functions to GPolyline ===
google.maps.Polyline.prototype.Distance = google.maps.Polygon.prototype.Distance;
google.maps.Polyline.prototype.GetPointAtDistance = google.maps.Polygon.prototype.GetPointAtDistance;
google.maps.Polyline.prototype.GetPointsAtDistance = google.maps.Polygon.prototype.GetPointsAtDistance;