Can not achieve a good closed loop in dataset

[wds01060202]

Hey，Dr.Urban
I tried the dataset（outdoor_large_loop）from your project website.It's a nice dataset ,I get a good Trajectory .But unfortunately，it can not achieve a good closed loop in the dataset .I also try the big vocabulary of ORB_SLAM2, but The result is same. So i want to know the Possible reason led to the fail
sclosed loop? What can I do to overcome it?

Any help(new version or something else) will be greatful!!
sincerely!

[FookSong]

More try，something would be different.
Try to change the parameter in .yaml，modify the fastth or extract different number features may be useful.!