Question about global map scale adjustment and local map scale consistency

[door-to-moon]

First of all, thank you very much for your great work. Your paper has been an perdect resource for my study of SLAM.
I’m a master’s student working in an aerial robotics lab, and I’ve recently started studying SLAM. I’m currently trying to understand and implement your CCM-SLAM using ROS as part of my learning process.

While studying the paper and testing the implementation, I came across two questions regarding the global and local map scales:

I have two questions regarding the global map and scale handling:

1. As described in the paper, the initial global map appears to adopt the scale of the first local map. However, when multiple local maps are merged by global bundle adjustment, is the global scale recalculated or adjusted based on the merged maps? In other words, is the scale of the global map changed by map merge?

2. When a local map receives Keyframes and Map points from the global map and updates its own map, does the scale of the local map remain unchanged(No scale changes)? Or is there any implicit scale adjustment applied to the local map as a result of this update?

I understand that SIM(3) transformations are used to align maps between local map and global map. However, I’m curious whether these transformations imply that the local map’s internal scale is also updated, or whether it always keeps its original scale.

Thank you very much for your time and for your contributions to the field. Your work is helping me a lot in my learning journey.

Best regards,