STA-VPR: Spatio-temporal Alignment for Visual Place Recognition
This work addresses viewpoint and condition invariance in visual place recognition, which is crucial for robotics and autonomous systems, but it is incremental as it builds on existing CNN-based methods.
The authors tackled the problem of visual place recognition under large viewpoint and appearance changes by splitting holistic mid-layer CNN features into local features and using adaptive dynamic time warping for spatial alignment, achieving significant improvements over CNN-based methods and outperforming several state-of-the-art methods on five datasets while maintaining good run-time performance.
Recently, the methods based on Convolutional Neural Networks (CNNs) have gained popularity in the field of visual place recognition (VPR). In particular, the features from the middle layers of CNNs are more robust to drastic appearance changes than handcrafted features and high-layer features. Unfortunately, the holistic mid-layer features lack robustness to large viewpoint changes. Here we split the holistic mid-layer features into local features, and propose an adaptive dynamic time warping (DTW) algorithm to align local features from the spatial domain while measuring the distance between two images. This realizes viewpoint-invariant and condition-invariant place recognition. Meanwhile, a local matching DTW (LM-DTW) algorithm is applied to perform image sequence matching based on temporal alignment, which achieves further improvements and ensures linear time complexity. We perform extensive experiments on five representative VPR datasets. The results show that the proposed method significantly improves the CNN-based methods. Moreover, our method outperforms several state-of-the-art methods while maintaining good run-time performance. This work provides a novel way to boost the performance of CNN methods without any re-training for VPR. The code is available at https://github.com/Lu-Feng/STA-VPR.