func NewPointsIndex(resolution Meters) *PointsIndex {
	newSet := func() interface{} {
		return newSet()
	}

	return &PointsIndex{newGeoIndex(resolution, newSet), make(map[string]Point)}
}
func NewPointsIndex(resolution Meters) *PointsIndex {
	newSet := func() interface{} {
		return newSet()
	}

	return &PointsIndex{newGeoIndex(resolution, newSet), make(map[string]Point)}
}
// NewPointsIndex creates new PointsIndex that maintains the points in each cell.