Gmapping - entropy has fixed value

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Hi everyone!

I run gmapping with Hokuyo laser scanner. I published the transforms this way, so I can't really estimate the position in the map, but it works for a static position, and if I move the laser it updates the map, assuming the laser is in the same position. The transforms:

<launch>
  <node pkg="tf" type="static_transform_publisher" name="odom_to_base_link" args="0 0 0 0 0 0 odom base_link 100" />
  <node pkg="tf" type="static_transform_publisher" name="US6" args="0 7 2 1.5708 0 0 base_link laser 100" />
</launch>

When I run gmapping and do rostopic echo /slam_gmapping/entropy, this is what it ALWAYS outputs, even if the map changes and becomes more occupied: data: 3.4119738166.

If you know how to update the entropy with the movement of the laser, I would appreciate your help! Thank you!