similarity score between two irrelevant frame

[ycx-max]

Than you for your great work! I ran your soild code to test the similarity between two frames in kitti.In most cases, it seems perfect.But i found that the similarity score remains high even if the two frames are not relevant.Take 001812 and 000829 in kitti 08 for example, they are not the same scene,but the output similarity score is 0.82.What's the matter?