add two laser for navigation

edit

Below is the configuration that I used to successfully launch two observation sources in my costmaps. I'd guess you may have forgotten to add the second source to the list of sources in the observation_sources parameter.

observation_sources: sick_lms_1 sick_lms_2

sick_lms_1: {sensor_frame: sick_1,
        data_type: LaserScan,
        topic: /scan_1,
        expected_update_rate: 0.4,
        observation_persistence: 0.0,
        marking: true,
        clearing: true,
        min_obstacle_height: 0.0,
        max_obstacle_height: 2.0,
        obstacle_range: 9.0,
        raytrace_range: 10.0}

sick_lms_2: {sensor_frame: sick_2,
        data_type: LaserScan,
        topic: /scan_2,
        expected_update_rate: 0.4,
        observation_persistence: 0.0,
        marking: true,
        clearing: true,
        min_obstacle_height: 0.0,
        max_obstacle_height: 2.0,
        obstacle_range: 9.0,
        raytrace_range: 10.0}