# Unsupervised Learning Methods for Visual Place Recognition in Discretely and Continuously Changing Environments

arXiv: https://arxiv.org/abs/2001.08960 · HTML: https://mlsanity.com/paper/2001.08960/

## Key facts

- Cited by 14 papers in the map (data through 14 Oct 2026).
- First posted on arXiv 24 Jan 2020.

## Built on by (most cited first, 14 of 14)

- [Where is your place, Visual Place Recognition?](https://mlsanity.com/paper/2103.06443/) (2021)
- [Hyperdimensional computing as a framework for systematic aggregation of image descriptors](https://mlsanity.com/paper/2101.07720/) (2021)
- [Visual Place Recognition: A Tutorial](https://mlsanity.com/paper/2303.03281/) (2023)
- [What makes visual place recognition easy or hard?](https://mlsanity.com/paper/2106.12671/) (2021)
- [Place recognition survey: An update on deep learning approaches](https://mlsanity.com/paper/2106.10458/) (2021)
- [Beyond ANN: Exploiting Structural Knowledge for Efficient Place Recognition](https://mlsanity.com/paper/2103.08366/) (2021)
- [Unsupervised Complementary-aware Multi-process Fusion for Visual Place Recognition](https://mlsanity.com/paper/2112.04701/) (2021)
- [Self-Supervised Domain Calibration and Uncertainty Estimation for Place Recognition](https://mlsanity.com/paper/2203.04446/) (2022)
- [Boosting Performance of a Baseline Visual Place Recognition Technique by Predicting the Maximally Complementary Technique](https://mlsanity.com/paper/2210.07509/) (2022)
- [A Coarse-to-Fine Place Recognition Approach using Attention-guided Descriptors and Overlap Estimation](https://mlsanity.com/paper/2303.06881/) (2023)
- [NocPlace: Nocturnal Visual Place Recognition via Generative and Inherited Knowledge Transfer](https://mlsanity.com/paper/2402.17159/) (2024)
- [Adaptive Thresholding for Visual Place Recognition using Negative Gaussian Mixture Statistics](https://mlsanity.com/paper/2512.09071/) (2025)
- [Route-MHT: Multimodal Transformer Guardrails for Thermal Visual Place Recognition](https://mlsanity.com/paper/2607.04745/) (2026)
- [Are Visual Place Recognition Models Recognizing Places or Conditions? Distractor-Augmented Evaluation and Condition Suppression](https://mlsanity.com/paper/2608.06847/) (2026)

## Abstract (arXiv)

Visual place recognition in changing environments is the problem of finding matchings between two sets of observations, a query set and a reference set, despite severe appearance changes. Recently, image comparison using CNN-based descriptors showed very promising results. However, existing experiments from the literature typically assume a single distinctive condition within each set (e.g., reference: day, query: night). We demonstrate that as soon as the conditions change within one set (e.g., reference: day, query: traversal daytime-dusk-night-dawn), different places under the same condition can suddenly look more similar than same places under different conditions and state-of-the-art approaches like CNN-based descriptors fail. This paper discusses this practically very important problem of in-sequence condition changes and defines a hierarchy of problem setups from (1) no in-sequence changes, (2) discrete in-sequence changes, to (3) continuous in-sequence changes. We will experimentally evaluate the effect of these changes on two state-of-the-art CNN-descriptors. Our experiments emphasize the importance of statistical standardization of descriptors and shows its limitations in case of continuous changes. To address this practically most relevant setup, we investigate and experimentally evaluate the application of unsupervised learning methods using two available PCA-based approaches and propose a novel clustering-based extension of the statistical normalization.