Kinect PointCloud values [closed]

edit

Hello, I'm using depth/points topic published by kinect controller gazebo_ros_openni_kinect. My problem is that, even if an obstacle is set at distance 2.0, selecting the minimum depth point (no other obstacles in the scene) it always returns 1.0 depth (and relatives x-y coords). Now, all these coords should be in meters, so I can't reach my objective of obtaining the coord of the mimimum depth point in the scene (for obstacle avoidance purposes). Thank you.

EDIT: An other big problem is that, moving the robot, this depth measurement changes only when it is really close to the obstacle! How can I solve it?

EDIT #2: The .xacro of the kinect is:

    <gazebo reference="objective">
        <sensor:camera name="cam_sensor">
            <updateRate>20.0</updateRate>
<!--            <imageFormat>B8G8R8</imageFormat>-->
            <imageSize>640 480</imageSize>
            <hfov>58</hfov>
            <nearClip>0.1</nearClip>
            <farClip>100</farClip>
            <controller:gazebo_ros_openni_kinect name="kin_controller" plugin="libgazebo_ros_openni_kinect.so">
                <frameName>generic_camera_link</frameName>
                <cameraName>kinect</cameraName>
                <alwaysOn>true</alwaysOn>
<!--                <CxPrime>320</CxPrime>-->
<!--                <Cx>320</Cx>-->
<!--                <Cy>240</Cy>-->
<!--                <focal_length>320</focal_length> <! image_width / (2*tan(hfov_radian /2)) >-->
                <imageTopicName>rgb/image</imageTopicName>
                <cameraInfoTopicName>rgb/camera_info</cameraInfoTopicName>
                <depthImageTopicName>depth/image</depthImageTopicName>
                <depthImageCameraInfoTopicName>depth/camera_info</depthImageCameraInfoTopicName>
                <pointCloudTopicName>points</pointCloudTopicName>
                <pointCloudCutoff>0.5</pointCloudCutoff>
            </controller:gazebo_ros_openni_kinect>  
        </sensor:camera>

which is included in another .xacro file (and then in a .launch):

<kinectSensor parent="chassis_link"><origin xyz="0.05 0 ${chassis_height+topTable_height+topCyl_height+laserCylHeight+laserBaseSide+0.015}" rpy="0 0 0"/></kinectSensor>

EDIT #3: Could it be the plane on which the obstacle and the robot stay which always gives depth = 1.0? How can I solve, if it is the problem?

EDIT #4: That's what I obtain from rviz: http://imageshack.us/photo/my-images/27/screenshotxyt.png/ It seems everything has the same depth... and the floor is a big problem!