Localization

Introduction

This module provides localization services. There are two ways in which localization is provided:

• The RTK (Real Time Kinematic) based method which incorporates GPS and IMU (Inertial Measurement Unit) information
• The multi-sensor fusion method which incorporates GPS, IMU, and LiDAR information.

Directory Structure

modules/localization/
├── BUILD
├── common          // common function, data structure and gflags definition
├── conf
├── cyberfile.xml
├── dag
├── launch
├── msf             // msf localization implementation
├── ndt             // ndt localization implementation
├── proto
├── README_cn.md
├── README.md
├── rtk             // rtk localization implementation
└── testdata

Modules

Component

• apollo::localization::MSFLocalizationComponent
• apollo::localization::NDTLocalizationComponent
• apollo::localization::RTKLocalizationComponent

Input

In the provided RTK localization method, there are two inputs:

• GPS - The Global Positioning System
• IMU - Inertial Measurement Unit

In the multi-sensor fusion localization method, there are three inputs:

• GPS - The Global Positioning System
• IMU - Inertial Measurement Unit
• LiDAR - Light Detection And Ranging Sensor

Output

An object instance defined by Protobuf message LocalizationEstimate, which can be found in file localization/proto/localization.proto.

How to Launch

cyber_launch start modules/localization/launch/msf_localization.launch

### Output
An object instance defined by Protobuf message `LocalizationEstimate`, which can be found in file `common_msgs/localization_msgs/localization.proto`.

### configs

| file path                                                        | type / struct                            | Description                |
| ------------------------------------------------------------- | ------------------------------------------- | -------------------------- |
| `modules/localization/conf/localization_config.pb.txt`        | `apollo::localization::LocalizationConfig`  | localization type config   |
| `modules/localization/conf/navi_localization_config.pb.txt`   | `apollo::localization::LocalizationConfig`  | localization type config   |
| `modules/localization/conf/rtk_localization.pb.txt`           | `apollo::localization::rtk_config::Config`  | rtk mode config            |
| `modules/localization/conf/localization.conf`                 | `gflags`                                    | gflags config              |

### Flags

| flagfile                                             | type | Description                    |
| ---------------------------------------------------- | ---- | ------------------------------ |
| `modules/localization/common/localization_gflags.cc` | `cc` | localization flags header      |
| `modules/localization/common/localization_gflags.h`  | `h`  | localization flags define      |

### How to Launch

```bash
cyber_launch start modules/drivers/camera/launch/rtk_localization.launch  // run rtk localization
cyber_launch start modules/drivers/camera/launch/ndt_localization.launch  // run ndt localization
cyber_launch start modules/drivers/camera/launch/msf_localization.launch  // run msf localization

Implementing Localization

Currently the RTK based localization is implemented in class RTKLocalization. If you are implementing a new localization method, for example, FooLocalization, you would need to perform the following steps:

1. In localization_config.proto, add a value FOO to the LocalizationType enum type

2. Go to the modules/localization directory, and create a foo directory. In the foo directory, implement the class FooLocalization by following the code in the RTKLocalization class in the rtk directory. FooLocalization has to be a subclass of LocalizationBase. Also create a file foo/BUILD by following the file rtk/BUILD

3. You need to register the FooLocalization class in the function Localization::RegisterLocalizationMethods(), which is located in the localization.cc file. You can register it by inserting the following code at the end of the function:

 localization_factory_.Register(LocalizationConfig::FOO, []()->LocalizationBase* { return new FooLocalization(); });

4. Make sure your code compiles by including the header files that defines class FooLocalization

5. Now you can go back to the apollo root directory and build your code with command bash apollo.sh build in source env; while buildtool build -p modules/localization in package management env.

Reference

For more information, refer to

Guowei Wan, Xiaolong Yang, Renlan Cai, Hao Li, Yao Zhou, Hao Wang, Shiyu Song. "Robust and Precise Vehicle Localization Based on Multi-Sensor Fusion in Diverse City Scenes," 2018 IEEE International Conference on Robotics and Automation (ICRA), Brisbane, QLD, 2018, pp. 4670-4677. doi: 10.1109/ICRA.2018.8461224. link