# Exercise 3.2 ROS navigation

**URL:** <https://get-help.theconstruct.ai/t/exercise-3-2-ros-navigation/24545>\
**Category:** Uncategorized\
**Created:** [May 24, 2023, 10:54am UTC](https://get-help.theconstruct.ai/t/exercise-3-2-ros-navigation/24545 "2023-05-24T10:54:05Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![ROSBUILD](https://get-help.theconstruct.ai/letter_avatar_proxy/v4/letter/r/a4c791/32.png) [@ROSBUILD](https://get-help.theconstruct.ai/u/ROSBUILD)\
**Post date:** [May 24, 2023, 10:54am UTC](https://get-help.theconstruct.ai/t/exercise-3-2-ros-navigation/24545/1 "2023-05-24T10:54:05Z")

</div>

where do i find this files in the workspace, I am not able to locate this in catkin\_ws

 ![image](https://get-help.robotigniteacademy.com/uploads/default/original/2X/b/bae2a77a88ac62aaa3f0071a0208e64613de8302.png)  
and even when i am creating any package in catkin\_ws and trying to launch any file made by me,its always throw error as no such file and package is there and all , whats the problem here going on?

---

<div class="post-metadata">

**Author:** ![rzegers](https://get-help.theconstruct.ai/user_avatar/get-help.theconstruct.ai/rzegers/32/7010_2.png) [@rzegers](https://get-help.theconstruct.ai/u/rzegers)\
**Post date:** [May 25, 2023, 8:13am UTC](https://get-help.theconstruct.ai/t/exercise-3-2-ros-navigation/24545/2 "2023-05-25T08:13:44Z")

</div>

Hello @ROSBUILD,

here is thes short answer:

Run this command to see the contents of that file:

```auto

cat /home/simulations/public_sim_ws/src/all/husky/husky/husky_navigation/launch/amcl.launch

```

Here is the long answer:

You can use the `rospack find [package_name]` command to get the the path to a package.  
Thus, to get the path to the husky\_navigation package you would type:

```auto
rospack find husky_navigation

```

This will show this path:

```auto
/home/simulations/public_sim_ws/src/all/husky/husky/husky_navigation

```

you can see the directories inside that package by typing:

```auto
ls /home/simulations/public_sim_ws/src/all/husky/husky/husky_navigation

```

as you can see there is a launch directory:

```auto
CHANGELOG.rst CMakeLists.txt config launch maps package.xml

```

look at the files inside the launch directory (since we want to display the content of a launch file):

```auto
ls /home/simulations/public_sim_ws/src/all/husky/husky/husky_navigation/launch

```

You will see that this directory has the launch file that you are looking for (among other launch files):

```auto
amcl.launch exploration_demo.launch move_base.launch
amcl_demo.launch gmapping.launch move_base_demo.launch
exploration.launch gmapping_demo.launch move_base_mapless_demo.launch

```

Finally to see the contents of this amcl launch file use the cat command, providing the path to the file like this:

```auto
cat /home/simulations/public_sim_ws/src/all/husky/husky/husky_navigation/launch/amcl.launch

```

For completeness, below a (shorter version of) the content of that launch file:

```auto
<?xml version="1.0"?>
<launch>

  <arg name="use_map_topic" default="true"/>
  <arg name="scan_topic" default="scan" />

  <node pkg="amcl" type="amcl" name="amcl">
    <param name="use_map_topic" value="$(arg use_map_topic)"/>
    <!-- Publish scans from best pose at a max of 10 Hz -->
    <param name="odom_model_type" value="diff"/>
    <param name="odom_alpha5" value="0.1"/>
    <param name="gui_publish_rate" value="10.0"/>
    <param name="laser_max_beams" value="60"/>
    <param name="laser_max_range" value="12.0"/>
    <param name="min_particles" value="500"/>
    <param name="max_particles" value="2000"/>
    <param name="kld_err" value="0.05"/>
    <param name="kld_z" value="0.99"/>
    <param name="odom_alpha1" value="0.2"/>
    <param name="odom_alpha2" value="0.2"/>
    <!-- translation std dev, m -->
    <param name="odom_alpha3" value="0.2"/>
    <param name="odom_alpha4" value="0.2"/>
    <param name="laser_z_hit" value="0.5"/>
    <param name="laser_z_short" value="0.05"/>
    <param name="laser_z_max" value="0.05"/>
    <param name="laser_z_rand" value="0.5"/>
    <param name="laser_sigma_hit" value="0.2"/>
    <param name="laser_lambda_short" value="0.1"/>
    <param name="laser_model_type" value="likelihood_field"/>
    <!-- <param name="laser_model_type" value="beam"/> -->
    <param name="laser_likelihood_max_dist" value="2.0"/>
    <param name="update_min_d" value="0.25"/>
    <param name="update_min_a" value="0.2"/>
    <param name="odom_frame_id" value="odom"/>
    <param name="resample_interval" value="1"/>
    <!-- Increase tolerance because the computer can get quite busy -->
    <param name="transform_tolerance" value="1.0"/>
    <param name="recovery_alpha_slow" value="0.0"/>
    <param name="recovery_alpha_fast" value="0.0"/>
    <remap from="scan" to="$(arg scan_topic)"/>
  </node>

</launch>

```

Hope this helps,

Roberto