google maps middle of a polyline (centroid?)

Question

I have a list of polylines, just like google maps does when I click on the polyline I want an infowindow to show up just where I clicked, and it works just fine with this fu

Answer 1

From http://www.geocodezip.com/v3_polyline_example_geodesic_proj.html

Without extensions and assuming the polyline is a straight line.

It is possible to convert the lat/lng coordinates to point plane (x,y) postions and calculate the average between the two. This will give you a central pixel position. You can then convert this position back to a latlng for map plotting.

var startLatLng = startMarker.getPosition(); 
var endLatLng = endMarker.getPosition(); 
var startPoint = projection.fromLatLngToPoint(startLatLng); 
var endPoint = projection.fromLatLngToPoint(endLatLng); 
// Average 
var midPoint = new google.maps.Point( 
    (startPoint.x + endPoint.x) / 2, 
    (startPoint.y + endPoint.y) / 2); 
// Unproject 
var midLatLng = projection.fromPointToLatLng(midPoint); 
var midMarker = createMarker(midLatLng, "text");

More information on changing the projection http://code.google.com/apis/maps/documentation/javascript/reference.html#Projection