Robot localization and Landmarks

edit

I am using the robot_localization package on a turtlebot running ROS Indigo. I would like the turtlebot to autonomously navigate a space and update it's position based on AprilTag landmarks. It seems that the way to do this is to take advantage of a map frame. However, when I publish landmark data, the map frame does not update in the discrete jumps I am hoping for. Perhaps I am doing something wrong with the launch file or with the way I am publishing tag data? How do you make sure robot_localization pays attention to the tags? Should I be using the set_pose service instead, or is that only meant to set initial position?

EDIT: Ideally, I would like the map frame to be updated discontinuously when it encounters a landmark, much as the GPS package in robot_localization allows the map frame to be discretely updated. The data published on the apriltags topic is relative to the map frame. There is not currently a transform between the apriltags frame and odom (I am a bit uncertain as to how to approach this). Will publishing a transform as well give discrete updates to position?

FINAL EDIT: Looks like figuring out the tf transformation is the key. I added a tf.TransformBroadcaster to go along with the apriltags publisher, and there were discrete updates; however, it doesn't seem to do what I want with non-zero data. If I publish a zeroed out message and a zeroed out transform, it zeros out the turtlebot. But if I do anything else, the map doesn't update.

My launch file looks like this:

<launch>

<!-- Set up the odom frame (local, continuous navigation) --> 
<node pkg="robot_localization" type="ekf_localization_node" name="ekf_localization_imu" respawn="true" output="screen">
    <param name="map_frame" value="map"/>
    <param name="odom_frame" value="odom"/>
    <param name="base_link_frame" value="base_footprint"/>      
    <param name="world_frame" value="odom"/>                
    <param name="two_d_mode" value="true"/>

    <param name="imu0" value="imu_data"/>
    <rosparam param="imu0_config">
        [false, false, false,
        false, false, true,
        false, false, false,
        false, false, true,
        true, false, false]
    </rosparam>
    <param name="imu0_differential" value="false"/>

    <param name="odom0" value="odom"/>
    <rosparam param="odom0_config">
        [false, false, false,
        false, false, false,
        true, true, false,
        false, false, true,
        false, false, false]
    </rosparam>
    <param name="odom0_differential" value="true"/>

</node>

<!-- Set up the map frame (global, includes jumps) --> 
<node pkg="robot_localization" type="ekf_localization_node" name="ekf_localization_map" respawn="true" output="screen">
    <param name="map_frame" value="map"/>
    <param name="odom_frame" value="odom"/>
    <param name="base_link_frame" value="base_footprint"/>      
    <param name="world_frame" value="map"/>                
    <param name="two_d_mode" value="true"/>

    <param name="imu0" value="imu_data"/>
    <rosparam param="imu0_config">
        [false, false, false,
        false, false, true,
        false, false, false,
        false, false, true,
        true, false, false]
    </rosparam>
    <param name="imu0_differential" value="false"/>

    <param name="odom0" value="odom"/>
    <rosparam param="odom0_config">
        [false, false, false,
        false, false, false,
        true, true, false,
        false, false, true,
        false, false, false]
    </rosparam>
    <param name="odom0_differential" value="true"/>

    <param name="pose0" value = "apriltags"/>
    <rosparam param="pose0_config">
        [true, true, false, 
        false, false, false, 
        false, false, false, 
        false, false, false]
    </rosparam>
    <param name="pose0_differential" value ...