2D map with velodyne and octomap_server

edit

Hi, I have a Velodyne VLP-16 on a robot and I am trying to build a 2D map from the velodyne point clouds using octomap_server. The velodyne point clouds are published on topic velodyne_points. I have odometry from a transform from world -> base_link frames. Since octomap_server requires a transform from sensor data frame to global map frame, I published a static transform from base_link -> velodyne and then remapped the cloud_in topic to velodyne_points as follows:

<node pkg="tf" type="static_transform_publisher" name="velodyne_tf" args="0 0 0 0 0 0 base_link velodyne 100" /> 
<node pkg="octomap_server" type="octomap_server_node" name="octomap_server">
     <param name="resolution" value="0.05" />
     <param name="frame_id" type="string" value="world" />
     <param name="sensor_model/max_range" value="15.0" />
     <param name="occupancy_min_z" value="0.05" />
     <param name="occupancy_max_z" value="0.5" />
     <remap from="cloud_in" to="velodyne_points" />
</node>

However, no map is published. When I view the tf tree it is world -> base_link -> velodyne. Any ideas as to why this isn't working?

Thank you!