// generate a grid map with geoJSON format
function generateGridMapGeoJSON(collection, x1, y1, x2, y2, indexType) {
    var step_x = (x2 - x1) / 100.0;
    var step_y = (y2 - y1) / 100.0;

    collection.drop();
    collection.ensureIndex({loc: indexType});

    for( var i = x1; i < x2; ) {
        var bulk = collection.initializeUnorderedBulkOp();

        for(var j = y1; j < y2; ) {
            bulk.insert({loc: {type: "Point", coordinates: [i, j]}});
            j = j + step_y;
        }
        bulk.execute( {w: 1});
        i = i + step_x;
    }
    collection.getDB().getLastError();
}

// define the area for the map in collection
var x_min = -0.005;
var x_max =  0.005;
var y_min = -0.005;
var y_max =  0.005;

// define the area to run query from
// leave 1/7 out on each edge to make sure query are not run out of bound
var x_query_min = x_min * (6.0/7.0);
var x_query_max = x_max * (6.0/7.0);
var y_query_min = y_min * (6.0/7.0);
var y_query_max = y_max * (6.0/7.0);

// query will run from a 13x13 grid
var x_query_step = (x_query_max - x_query_min) / 13.0;
var y_query_step = (y_query_max - y_query_min) / 13.0;

var collection = db.getCollection("geo_near_test")
generateGridMapGeoJSON(collection,  x_min, y_min, x_max, y_max, "2dsphere");

collection.find({loc: { $near: {$geometry: {type: "Point", coordinates:  [ 0.000329670329670329, 0.0009890109890109888 ] }}}} ).limit(1)