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The problem -> I need to find out the percentage of overlap between two routes.

Solution tried so far -> I tried passing the origin and destination (along with the key of course) to the following URL

https://maps.googleapis.com/maps/api/directions/json

and parsed the json response accordingly. Here is my code snippet - 

$endpoint = 'https://maps.googleapis.com/maps/api/directions/json?origin='.$startLatitude1.','.$startLongitude1.'&destination='.$endLatitude1.','.$endLongitude1.'&key='.$mykey;
$json1 = file_get_contents($endpoint.http_build_query(array())); //array is empty here
$data1 = json_decode($json1);

if ($data1->status === 'OK') {

    $endpoint = 'https://maps.googleapis.com/maps/api/directions/json?origin='.$startLatitude2.','.$startLongitude2.'&destination='.$endLatitude2.','.$endLongitude2.'&key='.$mykey;
    $json2 = file_get_contents($endpoint.http_build_query(array())); //array is empty here
    $data2 = json_decode($json2);

    $polyline = array();

    if ($data2->status === 'OK') {
        $route2 = $data2->routes[0];
        foreach ($route2->legs as $leg2) {
            foreach ($leg2->steps as $step2) {
                $polyline[$step2->polyline->points] = $step2->distance->value;
                }
            }
        }

        $overlap = 0;
        $totalDistance = 0;
        $route1 = $data1->routes[0];
        foreach ($route1->legs as $leg1) {
        $totalDistance = $leg1->distance->value;
            foreach ($leg1->steps as $step1) {
                if (array_key_exists($step1->polyline->points, $polyline)) {
                    $overlap = $overlap + $step1->distance->value;
                }
            }
        }
        echo 'Total Distance -> '.$totalDistance;
        echo 'Overlap -> '.$overlap.'<br>';

}

So we are first traversing route 1 and storing the polylines as key in an associative array with distance as the value. Next we traverse route 2 and check if polylines from route 2 is already present in the associative array created earlier.

The problem -> This works until and unless the roads are straight. Let's assume there are 4 points - A, B, C, D and all are in a straight line in that order. Person X wants to go from A to D whereas person Y wants to go from B to C. So there is an overlap of B-C. But because the polylines will never match (origin and destination being different for X & Y), my code will not detect any overlap.

Any other way out?

Saurav
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  • I also referred to the link - https://jsfiddle.net/geocodezip/ko2gjrxp/5/ When I check it I do see they are getting the overlap perfectly. But they are referring to certain variables like 'segment' which is not there in json response and anyway this has to be server side code for me. – Saurav Mar 08 '17 at 10:39
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    related question: [How to find the overlap of polylines in order to draw the common segment as shaded on google maps](http://stackoverflow.com/questions/32230611/how-to-find-the-overlap-of-polylines-in-order-to-draw-the-common-segment-as-shad) – geocodezip Mar 08 '17 at 21:44
  • I have seen that but I was not able to add more than one link in my comment so dropped that reference. It refers to the jsfiddle code which is client side. I am looking for something server side. The jsfiddle code has something called 'segment' for each 'step' on the route but that is missing in the server side json response. – Saurav Mar 09 '17 at 06:40
  • See this - http://stackoverflow.com/questions/22450061/displaying-results-of-google-direction-web-service-without-using-javascript-api. The JS API and the Web service are returning different responses. Or are we saying the path in JS is essentially the decoded polyline from the service? – Saurav Mar 09 '17 at 09:30
  • @Saurav - Did you get any luck? please share if you found any solution, thanks much. +1 – Sachin Vairagi Apr 04 '17 at 05:06
  • no....not yet. I am decoding the polylines and then comparing but the whole thing is pathetically slow hence not usable. – Saurav Apr 05 '17 at 07:16

0 Answers0