Route Boxer

The RouteBoxer class generates a set of LatLngBounds objects that are guaranteed to cover every point within a specified distance of a path, such as that generated for a route by the DirectionsService class. The primary use case for this class is to support implementing Search along a route against a Spatial db that supports bounding box queries.

Note that it is not the intention of the class to limit the bounding boxes to only those regions within the specified distance of the route, which is not possible given that routes are not rectangular. Consequently searches performed using these bounding boxes may return results up to ~3x the given distance from the route (twice the distance across the diagonal of a square with sides of the given distance).

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How to use the class

To use the RouteBoxer class, first load the RouteBoxer.js file into your page:

<script type="text/javascript" src="http://google-maps-utility-library-v3.googlecode.com/svn/trunk/routeboxer/src/RouteBoxer.js"></script>

Then create a RouteBoxer object, and pass an array of google.maps.LatLng objects and a distance to the RouteBoxer.box() method. If implementing search along a route the overview_polyline property of agoogle.maps.DirectionsRoute object contains a suitable array of LatLng objects:

var directionService = new google.maps.DirectionsService();
var rboxer = new RouteBoxer();
var distance = 20; // km

directionService.route(request, function(result, status) {
  if (status == google.maps.DirectionsStatus.OK) {
  
    // Box the overview path of the first route
    var path = result.routes[0].overview_path;
    var boxes = routeBoxer.box(path, distance);
    
    for (var i = 0; i < boxes.length; i++) {
      var bounds = box[i];
      // Perform search over this bounds 
    }
  }
});

How the RouteBoxer class works

The RouteBoxer class generates the boxes for a route in a number of steps.

STEP 1:

STEP 2:

Every cell in the grid that the route intersects with is identified. To do this the vertices on the route polyline are traversed, and the cell containing each vertex is marked. If a cell that is marked does not share an edge with the cell for the previous vertex, the intermediate cells are also marked.

STEP 3:

STEP 4:

STEP 5: 

STEP 6:

STEP 7:

STEP 8:

STEP 9:

STEP 10:

The RouteBoxer class takes a path, such as the Polyline for a route generated by a Directions request, and generates a set of LatLngBounds objects that are guaranteed to contain every point within a given distance of that route. These LatLngBounds objects can then be used to generate requests to spatial search services that support bounds filtering (such as the Google Maps Data API) in order to implement search along a route. 

RouteBoxer overlays a grid of the specified size on the route, identifies every grid cell that the route passes through, and generates a set of bounds that cover all of these cells, and their nearest neighbours. Consequently the bounds returned will extend up to ~3x the specified distance from the route in places.

For a description and examples of how to use this library, check out the how-to.

class RouteBoxer

Constructor

Methods