AMCL: map and scan not in the same frame

I load the map (built by hector slam before) by map_server and my scan is in rosbag. When I play rosbag. The scan is in "scan" frame while the map is in "map" frame. How to solve the problem? I know that I also need odometry. But I dont understand how can this get a tf tree? AMCL only provide odom->map. Its not enough to get scan->map. I want to use AMCL to localize in the given map.