# Running the grasp\_object demo

**URL:** <https://forum.hello-robot.com/t/running-the-grasp-object-demo/764>\
**Category:** Ask\
**Created:** [July 6, 2023, 6:32pm UTC](https://forum.hello-robot.com/t/running-the-grasp-object-demo/764 "2023-07-06T18:32:27Z")\
**Posts on this page:** 1\
**Showing post:** 8

<div class="post-metadata">

**Author:** ![bshah](https://yyz2.discourse-cdn.com/flex030/user_avatar/forum.hello-robot.com/bshah/32/55_2.png) [@bshah](https://forum.hello-robot.com/u/bshah)\
**Post date:** [July 10, 2023, 11:11pm UTC](https://forum.hello-robot.com/t/running-the-grasp-object-demo/764/8 "2023-07-10T23:11:54Z")

</div>

Hi @sesem378, looking at the original warning “Could not get base to fixed frame transform […] when looking up transform from frame [base\_link] to frame [odom]”, I’d like to see what’s happening there. As you may know, `base_link` is the robot’s first frame and every other frame on the robot is defined with respect to that link. The `base_link` is rigidly attached to the mobile base, in between the two wheels. The `odom` frame, as defined by [REP 105](https://www.ros.org/reps/rep-0105.html), is fixed in the world and gives you an noisy estimate of where the robot has moved in the world. It’s the `laser_scan_matcher_node`’s job to publish the `base_link` to `odom` transform by looking at the 2D lidar and estimating how Stretch has moved. In `grasp_object.launch`, lines [29-31](https://github.com/hello-robot/stretch_ros/blob/0a44e0eca9597163968a8179f8e98061e122d4c6/stretch_demos/launch/grasp_object.launch#L29-L31) include that node.

Could you run the following command to see if TF2 knows about a transform between `base_link` and `odom`:

```auto
rosrun tf tf_echo base_link odom

```

On my robot, the output looks like:

> **Output**
>
> ```auto
> $ rosrun tf tf_echo base_link odom
> At time 1689029640.313
> - Translation: [0.004, 0.001, 0.000]
> - Rotation: in Quaternion [0.000, 0.000, -0.002, 1.000]
> in RPY (radian) [0.000, 0.000, -0.004]
> in RPY (degree) [0.000, 0.000, -0.248]
> At time 1689029641.038
> - Translation: [0.004, 0.001, 0.000]
> - Rotation: in Quaternion [0.000, 0.000, -0.002, 1.000]
> in RPY (radian) [0.000, -0.000, -0.005]
> in RPY (degree) [0.000, -0.000, -0.269]
> At time 1689029641.995
> - Translation: [0.005, 0.001, 0.000]
> - Rotation: in Quaternion [0.000, 0.000, -0.003, 1.000]
> in RPY (radian) [0.000, -0.000, -0.005]
> in RPY (degree) [0.000, -0.000, -0.307]
> 
> ```

Additionally, let’s verify that the `laser_scan_matcher_node` is alive using:

```auto
rosnode list

```

The output should be:

> **Output**
>
> ```auto
> $ rosnode list
> /aggregator_node
> /camera/realsense2_camera
> /camera/realsense2_camera_manager
> /configure_d435i
> /d435i_accel_correction
> /funmap
> /grasp_object
> /joint_state_publisher
> /laser_filter
> /laser_scan_matcher_node
> /lidar_node
> /robot_state_publisher
> /rosout
> /rviz_1689025409739790621
> /stretch_driver
> 
> ```

---

_[View the full topic](https://forum.hello-robot.com/t/running-the-grasp-object-demo/764)._