Mapping & Localization

1. Requirements

Before working with this repository, ensure that:

• ROS2 Jazzy is installed
• colcon is installed
• You are using a Linux environment, for example Ubuntu inside UTM

This README assumes ROS2 is installed under:

/opt/ros/jazzy

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1.1 Source ROS2 in each new terminal

ROS2 is not active automatically when a terminal is opened. Before using colcon or ros2 commands, run:

source /opt/ros/jazzy/setup.bash

This must be done in every new terminal unless you make it automatic.

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1.2 Optional automatic ROS2 sourcing

If you want ROS2 to always be available:

echo "source /opt/ros/jazzy/setup.bash" >> ~/.bashrc
source ~/.bashrc

You still need to source your workspace separately after building it.

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2. Setting Up a Local Workspace

All ROS2 development must happen inside a workspace that contains:

• src for packages
• build created by colcon
• install created by colcon
• log created by colcon

Your repositories must go inside src.

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2.1 Create the workspace structure

mkdir -p ~/mapping_ws/src
cd ~/mapping_ws/src

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2.2 Clone this repository and ap1_msgs into src

From inside ~/mapping_ws/src:

cd ~/mapping_ws/src

# Mapping and localization repo
git clone git@github.com:WE-Autopilot/mapping-and-localization.git

# Shared messages repo used across AP1
git clone git@github.com:WE-Autopilot/ap1_msgs.git

Resulting structure:

mapping_ws
  src
    mapping_and_localization
      mapping_and_localization_cpp
      mapping_localization_python
    ap1_msgs

All shared custom messages for AP1 should live in ap1_msgs. If you need a new message type, add it to ap1_msgs rather than creating a new message package inside this repository.

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2.3 Building the workspace

What building does

Running:

colcon build

makes colcon:

• Compile C plus plus code
• Install binaries into install
• Register Python entry points
• Generate environment setup scripts
• Enable ros2 run to find the nodes

You must build when:

• C plus plus code changes
• package.xml changes
• CMakeLists.txt changes
• setup.cfg entry points change

Build the workspace

cd ~/mapping_ws
source /opt/ros/jazzy/setup.bash
colcon build --symlink-install

Symlink mode is recommended for development.

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2.4 Source the workspace after building

To use your nodes:

source ~/mapping_ws/install/setup.bash

You must source the workspace:

• In new terminals
• After every colcon build
• Before running ros2 commands

Python code works as long as you have sourced the workspace once in that terminal. C plus plus requires sourcing after each rebuild.

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2.5 Optional automatic workspace sourcing

If you use this workspace every day:

echo "source ~/mapping_ws/install/setup.bash" >> ~/.bashrc
source ~/.bashrc

Make sure the order in your ~/.bashrc is:

source /opt/ros/jazzy/setup.bash
source ~/mapping_ws/install/setup.bash

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3. Repository Structure

mapping_and_localization
  mapping_and_localization_cpp
    CMakeLists.txt
    package.xml
    src
      <cpp_nodes>.cpp

  mapping_localization_python
    package.xml
    setup.cfg
    setup.py
    mapping_localization_python
      <python_nodes>.py

  .gitignore
  README.md

Only the two folders with package.xml are ROS2 packages inside this repository.

The ap1_msgs package is a separate repository at:

mapping_ws
  src
    ap1_msgs

It contains shared message definitions that can be used by any AP1 package. Add new messages there when needed.

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4. Working With the Two Packages

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4.1 C plus plus Package: mapping_and_localization_cpp

Adding a node

In CMakeLists.txt:

add_executable(localization_node src/localization_node.cpp)

ament_target_dependencies(localization_node
  rclcpp
)
install(TARGETS
  localization_node
  DESTINATION lib/${PROJECT_NAME}
)

Adding dependencies

In package.xml:

<depend>rclcpp</depend>
<depend>std_msgs</depend>

If your C plus plus node uses messages from ap1_msgs (e.g., #include "ap1_msgs/msg/..."), add:

<depend>ap1_msgs</depend>

In CMakeLists.txt:

find_package(rclcpp REQUIRED)
find_package(std_msgs REQUIRED)
find_package(ap1_msgs REQUIRED)  # Only if you use ap1_msgs

ament_target_dependencies(localization_node
  rclcpp
  std_msgs
  ap1_msgs        # Only if you use ap1_msgs
)

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4.2 Python Package: mapping_localization_python

Adding a node

In setup.cfg:

[options.entry_points]
console_scripts =
  pose_node = mapping_localization_python.pose_node:main

Dependencies

In package.xml:

<depend>rclpy</depend>
<depend>std_msgs</depend>

If your Python node uses messages from ap1_msgs, also add:

<depend>ap1_msgs</depend>

Python files live inside:

mapping_localization_python/mapping_localization_python/

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5. Running Nodes

You must source the workspace first:

source ~/mapping_ws/install/setup.bash

Run a C plus plus node:

ros2 run mapping_and_localization_cpp localization_node

Run a Python node:

ros2 run mapping_localization_python pose_node

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6. Development Workflow and Rebuild Rules

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6.1 When to Rebuild

What changed	Need colcon build --symlink-install	Reason
Python file (.py)	No	Symlink points to source file
Launch, YAML, configuration	No	Symlinks update instantly
C plus plus file (.cpp, .hpp)	Yes	Must recompile
package.xml	Yes	Metadata changed
CMakeLists.txt	Yes	Build system instructions changed
New Python node in setup.cfg	Yes	Must regenerate entry point
Editing setup.cfg text only	Usually no	Not used at runtime
Adding a new package	Yes	Build system must detect it

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6.2 Recommended Developer Workflow

Python workflow

1. Edit the Python file
2. Source the workspace once in any terminal
3. Run the node

No rebuild required unless adding new entry points.

C plus plus workflow

1. Edit the C plus plus file

2. Run:

   colcon build --symlink-install

3. Source again:

   source install/setup.bash

4. Run the node

After modifying package.xml, CMakeLists.txt, or setup.cfg

• Rebuild with symlink
• Source workspace
• Run the node

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7. Notes for Developers

• Only folders with package.xml are ROS2 packages
• build, install, log and .vscode should not be committed
• Always run colcon build from the workspace root, never inside a package
• Never run CMake manually
• Shared messages should live in ap1_msgs. If you need a new message type for mapping or localization, add it there and then depend on ap1_msgs in your package.