Add the save trajectory function

[Taeyoung96]

@TixiaoShan
Hi, Thanks for your great work.
I add some functions to save Trajectory in the txt file.
This file is in TUM format, so it could directly visualize using evo tool.

Below is a visualization of the results of the M2DGR dataset using evo tool.

I hope this PR is helpful.

Thanks,

[Stephen1e]

Hi bro, thanks for your work which helped me a lot, I wonder how you get the ground truth from the GNSS data of the M2DGR dataset, how to convert GNSS data to trajectory in TUM format?

[Taeyoung96]

@Stephen1e
Hi, the M2DGR dataset provides ground truth txt files on their repository.
These ground truth files are in TUM format already, so you could use them directly!

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[Taeyoung96]

@TixiaoShan
Could I ask you to merge this PR?

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.