t = db.geo9;
t.drop();

t.save({_id: 1, a: [10, 10], b: [50, 50]});
t.save({_id: 2, a: [11, 11], b: [51, 52]});
t.save({_id: 3, a: [12, 12], b: [52, 52]});

t.save({_id: 4, a: [50, 50], b: [10, 10]});
t.save({_id: 5, a: [51, 51], b: [11, 11]});
t.save({_id: 6, a: [52, 52], b: [12, 12]});

t.ensureIndex({a: "2d"});
t.ensureIndex({b: "2d"});

function check(field) {
    var q = {};
    q[field] = {$near: [11, 11]};
    arr = t.find(q).limit(3).map(function(z) {
        return Geo.distance([11, 11], z[field]);
    });
    assert.eq(2 * Math.sqrt(2), Array.sum(arr), "test " + field);
}

check("a");
check("b");