[proposal] updates regarding the map projection (add scale_factor and remove map_origin.altitude)

[YamatoAndo]

I propose two updates regarding the map projection.

1. add scale_factor to map_projector_info.yaml

Allow the map scale factor to be specified arbitrarily.
For example, in Japan, maps are often created with a scale factor of 0.9999, enabling the selection of a scale factor suitable for the region.
However, in the MGRS and UTM coordinate systems, the scale factor is defined as 0.9996.
Additionally, since the Local coordinate system cannot be converted to latitude and longitude, the scale factor is not necessary.
Therefore, in practice, the scale factor is only applied when using the Transverse Mercator coordinate system.

The specific code changes are planned as follows:

• add scale_factor to MapProjectorInfo.msg

# Projector type
string LOCAL = "Local"
...
geographic_msgs/GeoPoint map_origin
float32 scale_factor

• modify TransverseMercatorExact::UTM(); in transverse_mercator_projector.cpp

  ↓

TransverseMercatorExact(Constants::WGS84_a(), Constants::WGS84_f(), scale_factor);

If scale_factor is not specified, I would like to handle the scale factor as 0.9996, the same as before.

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2. remove map_origin.altitude from map_projector_info.yaml

We have previously allowed specifying altitude, but I plan to remove this.
Because the vertical_datum parameter is set to accept values like WGS84 or EGM2008, the reference point for altitude is inherently determined, making it correct to always set the altitude to 0.0.
Nevertheless, allowing altitude to be input may cause confusion about what value should be entered.

The specific code changes are planned as follows:
modify msg.map_origin.altitude = data["map_origin"]["altitude"].as<double>(); in map_projection_loader.cpp
↓

msg.map_origin.altitude = 0.0;

So, even if map_origin.altitude is specified as before, it will always be treated as 0.0.

※ Since geographic_msgs/GeoPoint map_origin will remain unchanged, there will actually be no changes made to MapProjectorInfo.msg

---

I plan to submit a Pull Request by early March.
Thank you for your support, and I look forward to your feedback!

[YamatoAndo]

Pull Requests

• feat(autoware_msg_msgs): add scale factor remove altitude autoware_msgs#121
• feat(projection): add_scale_factor autoware_lanelet2_extension#54
• feat(map_projection_loader): add scale_factor and remove altitude autoware_core#340

[YamatoAndo]

Merged!