The lidar is mounted sideways; restrict the FoV to the robot's front …

…arc, not the sensor's

turtlebot4_description/urdf/sensors/rplidar.urdf.xacro

@@ -36,11 +36,13 @@
 
   <gazebo reference="${name}_link">
     <!--
-      GPU Ray sensor plugin only supports 180 degrees, so limig to the front arc only
+      GPU Ray sensor plugin only supports 180 degrees, so limit to the "front" arc only
+      The lidar is actually mounted sideways on the robot, with +x to the left, so the
+      front arc is actually 0 to -pi
     -->
     <xacro:ray_sensor sensor_name="${name}" gazebo="${gazebo}" 
                   update_rate="62.0" visualize="1" 
-                  h_samples="640" h_res="1.0" h_min_angle="${-pi/2}" h_max_angle="${pi/2}" 
+                  h_samples="640" h_res="1.0" h_min_angle="${-pi}" h_max_angle="0" 
                   r_min="0.164" r_max="12.0" r_res="0.01">
                   <plugin name="dummy" filename="dummyfile"></plugin>
     </xacro:ray_sensor>