Alejandro Fontán

dblp:272/0628 · also Alejandro Fontan Villacampa · DBLP profile ↗
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8ranked-venue papers
4as first author
7since 2021 · last 2026
0000-0002-5909-8415ORCID · verified

Domains — the database's venue-derived domains; a paper can count in several

Artificial intelligence and machine learning · 6 · 4 first-author · 5 since 2021Systems, architecture and hardware · 4 · 2 first-author · 4 since 2021Graphics, computer vision, multimedia, augmented reality and games · 4 · 2 first-author · 3 since 2021
YearPublicationVenuePosition
2026 Robust Scene Coordinate Regression via Geometrically-Consistent Global Descriptors
abstract
Recent learning-based visual localization methods use global descriptors to disambiguate visually similar places, but existing approaches often derive these descriptors from geometric cues alone (e.g., covisibility graphs), limiting their discriminative power and reducing robustness in the presence of noisy geometric constraints. We propose an aggregator module that learns global descriptors consistent with both geometrical structure and visual similarity, ensuring that images are close in descriptor space only when they are visually similar and spatially connected. This corrects erroneous associations caused by unreliable overlap scores. Using a batch-mining strategy based solely on the overlap scores and a modified contrastive loss, our method trains without manual place labels and generalizes across diverse environments. Experiments on challenging benchmarks show substantial localization gains in large-scale environments while preserving computational and memory efficiency. Code is available at github.com/sontung/robust_scr.
Son Tung Nguyen, Alejandro Fontán, Michael Milford, Tobias Fischer 0001
WACV2
2025 VSLAM-LAB: A Comprehensive Framework for Visual SLAM Methods and Datasets
abstract
Visual Simultaneous Localization and Mapping (VSLAM) research faces significant challenges due to fragmented toolchains, complex system configurations, and inconsistent evaluation methodologies. To address these issues, we present VSLAM-LAB, a unified framework designed to streamline the development, evaluation, and deployment of VSLAM systems. VSLAM-LAB simplifies the entire workflow by enabling seamless compilation and configuration of VSLAM algorithms, automated dataset downloading and preprocessing, and standardized experiment design, execution, and evaluation. All of these features are accessible through a single command-line interface. The framework supports a wide range of VSLAM systems and datasets, offering broad compatibility and extendability while promoting reproducibility through consistent evaluation metrics and analysis tools. By reducing implementation complexity and minimizing configuration overhead, VSLAM-LAB empowers researchers to focus on advancing VSLAM methodologies and accelerates progress toward scalable, real-world solutions. We demonstrate the ease with which user-relevant benchmarks can be created: here, we introduce difficulty-level-based categories, but one could envision environment-specific or condition-specific categories.
Alejandro Fontán, Tobias Fischer 0001, Javier Civera 0001, Michael Milford
IROS1
2025 Image-Based Relocalization and Alignment for Long-Term Monitoring of Dynamic Underwater Environments
abstract
Effective monitoring of underwater ecosystems is crucial for tracking environmental changes, guiding conservation efforts, and ensuring long-term ecosystem health. However, automating underwater ecosystem management with robotic platforms remains challenging due to the complexities of underwater imagery, which pose significant difficulties for traditional visual localization methods. We propose an integrated pipeline that combines Visual Place Recognition (VPR), feature matching, and image segmentation on images extracted from video sequences. This method enables robust identification of revisited areas, estimation of rigid transformations, and downstream analysis of ecosystem changes. Furthermore, we introduce the SQUIDLE+ VPR BenchmarkÐthe first large-scale underwater VPR benchmark designed to leverage an extensive collection of unstructured data from multiple robotic platforms, spanning time intervals from days to years. The dataset encompasses diverse trajectories with varying overlap and diverse seafloor types captured under different environmental conditions, including differences in depth, lighting, and turbidity. Our code is available at: https://github.com/bev-gorry/underloc.
Beverley Gorry, Tobias Fischer 0001, Michael Milford, Alejandro Fontán
IROS4
2024 Adaptive Outlier Thresholding for Bundle Adjustment in Visual SLAM
abstract
State-of-the-art V-SLAM pipelines utilize robust cost functions and outlier rejection techniques to remove incorrect correspondences. However, these methods are typically fine-tuned to overfit certain benchmarks and struggle to adapt effectively to changes in the application domain or environmental conditions. This renders them impractical for many robotic applications in which robustness in a wide variety of conditions is essential. In this paper we introduce a novel distribution-based approach for online outlier rejection that reduces the necessity for scene-specific fine-tuning while simultaneously improving the overall SLAM performance. Through experiments across 3 different public datasets, we show that our approach consistently outperforms state-of-the-art methods in various real-world settings. Our code is available at https://github.com/alejandrofontan/ORB_SLAM2_Distribution
Alejandro Fontán, Javier Civera 0001, Michael Milford
ICRA1
2024 FocusTune: Tuning Visual Localization through Focus-Guided Sampling
abstract
We propose FocusTune, a focus-guided sampling technique to improve the performance of visual localization algorithms. FocusTune directs a scene coordinate regression model towards regions critical for 3D point triangulation by exploiting key geometric constraints. Specifically, rather than uniformly sampling points across the image for training the scene coordinate regression model, we instead re-project 3D scene coordinates onto the 2D image plane and sample within a local neighborhood of the reprojected points. While our proposed sampling strategy is generally applicable, we showcase FocusTune by integrating it with the recently introduced Accelerated Coordinate Encoding (ACE) model. Our results demonstrate that FocusTune both improves or matches state-of-the-art performance whilst keeping ACE’s appealing low storage and compute requirements, for example reducing translation error from 25 to 19 and 17 to 15 cm for single and ensemble models, respectively, on the Cambridge Landmarks dataset. This combination of high performance and low compute and storage requirements is particularly promising for applications in areas like mobile robotics and augmented reality. We made our code available at https://github.com/sontung/focus-tune.
Son Tung Nguyen, Alejandro Fontán, Michael Milford, Tobias Fischer 0001
WACV2
2023 Motion-Bias-Free Feature-Based SLAM
Alejandro Fontán, Michael Milford, Javier Civera 0001
BMVC1
2021 DOT: Dynamic Object Tracking for Visual SLAM
abstract
In this paper we present DOT (Dynamic Object Tracking), a front-end that added to existing SLAM systems can significantly improve their robustness and accuracy in highly dynamic environments. DOT combines instance segmentation and multi-view geometry to generate masks for dynamic objects in order to allow SLAM systems based on rigid scene models to avoid such image areas in their optimizations.To determine which objects are actually moving, DOT segments first instances of potentially dynamic objects and then, with the estimated camera motion, tracks such objects by minimizing the photometric reprojection error. This short-term tracking improves the accuracy of the segmentation with respect to other approaches. In the end, only actually dynamicmasks are generated.We have evaluated DOT with ORB-SLAM 2 [1] in three public datasets. Our results show that our approach improves significantly the accuracy and robustness of ORB-SLAM2, especially in highly dynamic scenes.
Irene Ballester, Alejandro Fontán, Javier Civera 0001, Klaus H. Strobl, Rudolph Triebel
ICRA2
2020 Information-Driven Direct RGB-D Odometry
abstract
This paper presents an information-theoretic approach to point selection in direct RGB-D odometry. The aim is to select only the most informative measurements, in order to reduce the optimization problem with a minimal impact in the accuracy. It is usual practice in visual odometry/SLAM to track several hundreds of points, achieving real-time performance in high-end desktop PCs. Reducing their computational footprint will facilitate the implementation of odometry and SLAM in low-end platforms such as small robots and AR/VR glasses. Our experimental results show that our novel information-based selection criterion allows us to reduce the number of tracked points an order of magnitude (down to only 24 of them), achieving an accuracy similar to the state of the art (sometimes outperforming it) while reducing 10 times the computational demand.
Alejandro Fontán, Javier Civera 0001, Rudolph Triebel
CVPR1