Distance issue displayed during orbslam3 positioning

[silence-moon]

This is a very excellent project. When I was using my own camera for testing, I found that on the same road section, when using ORBSLAM3 to locate the composition, I was driving in a straight line to the end of the road, and then the lens rotated, resulting in information loss. After entering a new sub map, the length of the return path did not match the length when I just came over. What is the reason for this problem? I am very much looking forward to your answer.

[WFram]

Scale drift typical for monocular odometry