Michael Milford / SeqSLAM
Robot navigation · Research overview

SeqSLAM

Visual route recognition using image sequences

Sequence-based place recognition under appearance change and with low-resolution imagery.

Conceptual illustration of a familiar suburban route transformed from sunny day to rainy night
Conceptual illustration
ICRA 2012Recognition under appearance change
RSS 2012Low-information route recognition
IJRR 2013Expanded experimental study

SeqSLAM recognises previously visited places by matching image sequences. Introduced at ICRA 2012, it combines low-resolution image comparison, local contrast enhancement and temporal consistency to tolerate substantial appearance change. The RSS 2012 and IJRR 2013 studies examined recognition with severely reduced visual information. [S1][S3][S7]

01 / Foundational papers

The original SeqSLAM studies

Appearance-change recognition and the visual information required for route recognition.

ICRA 2012

Recognition under appearance change

SeqSLAM: Visual route-based navigation for sunny summer days and stormy winter nights

The original SeqSLAM paper introduced sequence-based route recognition under substantial changes in illumination and weather. Local comparison of image differences and temporal matching enabled recognition when individual images were ambiguous. [S1]

ICRA 2012 paper ↗
RSS 2012 · IJRR 2013

Recognition with limited visual information

Visual Route Recognition with a Handful of Bits
Vision-based place recognition: how low can you go?

The RSS study varied image resolution, bit depth, field of view and sequence length. Experiments included four-pixel images and two light sensors. The IJRR paper expanded the investigation to seven datasets, including compression, motion blur and failure cases. [S3][S7]

Research figure from the SeqSLAM presentation, slide 5. [S7]
IJRR 2013

Localisation using light sensors

Two single-pixel light sensors provided intensity sequences for indoor localisation. The figure shows the sensor apparatus and route across three building levels. [S7]

02 / Experiments

Visual recognition under appearance change

Image comparisons from the original SeqSLAM research.

Original research image panel from Michael Milford’s presentation. Labels identify matching and different locations.
The central challenge · 2012

Appearance change and perceptual ambiguity

Appearance change can reduce image similarity at the same location below that of different locations. SeqSLAM addresses this ambiguity using locally normalised image comparisons and sequence matching. [S1][S4]

Alderley Day and Night dataset. Credit: Michael Milford, Gordon Wyeth / QUT. Dataset.
Alderley, Queensland · original dataset

Alderley day and night traversals

The Alderley dataset contains repeated traversals under daytime and rainy night-time conditions. It evaluates recognition under changes in illumination, visibility and surface reflections. [S2]

03 / Interactive model

Sequence-matching demonstration

Compare single-image and sequence matching under noise and repeated scenery.

Interactive explanation

Sequence length and matching ambiguity

This synthetic difference matrix contains a route, noisy observations and occasional misleading matches. Change the sequence length and inspect the computed match. The white dashed line is known ground truth; the gold path is the selected candidate. Synthetic teaching example; the archival images above show the real visual challenge.

Preset
The text readout reports the sequence match and error.
Selected sequenceKnown correspondenceBrighter cells = better matches

The demo searches four straight-line speed hypotheses. Noise is deterministic so settings can be compared. It illustrates one part of the idea; it is not the complete SeqSLAM pipeline.

04 / Method

SeqSLAM processing stages

Image reduction, local normalisation, pairwise comparison and sequence search.

SeqSLAM pipeline illustrated as small images, pairwise comparisons, locally enhanced scores and a sequence trajectory01Reduce & normaliseKeep broad visual structure02Compare every pairBuild a difference matrix03Enhance locallyFind relative similarities04Search sequencesAccumulate ordered evidenceA route can be distinctive even when its individual views are ambiguous.
Sequence-recognition pipeline (schematic). [S1][S3]

Image preprocessing

Convert frames to low-resolution grayscale images and normalise local patches to reduce sensitivity to illumination. Resolution and patch size are configurable parameters. [S4][S9]

Difference-matrix enhancement

Compare query and reference images. Normalise each candidate score relative to nearby reference locations to identify locally distinctive matches. [S4][S19]

Sequence matching

Search the enhanced difference matrix for low-cost sequences across candidate relative traversal speeds. Apply a matching threshold to reject weak correspondences. [S4][S19]

Localisation output

The output associates observations with previously visited places or route segments. These correspondences can support localisation or loop closure within a larger navigation system. [S18][S25]

Before local contrast enhancement. SeqSLAM presentation, slide 4. [S1]
After local contrast enhancement. SeqSLAM presentation, slide 4. [S1]
05 / Software

OpenSeqSLAM2.0

A MATLAB toolbox for inspecting preprocessing, matching costs and sequence estimates.

OpenSeqSLAM2.0 interface montage. Ben Talbot, Sourav Garg and Michael Milford (2018). Project page. [S20]
06 / Development timeline

Development timeline

From low-resolution route recognition to adaptive, learned and application-specific extensions.

16 milestones shown

Before 2012Foundations
Background in visual route recognition

SeqSLAM builds on low-resolution navigation and earlier sequence-matching methods. Its approach combines whole-image comparison, local normalisation of matching scores and temporal consistency. [S3][S4]

SeqSLAM builds on low-resolution navigation and earlier sequence-matching methods.

2011–2012Foundations
SeqSLAM at ICRA 2012

The original SeqSLAM paper introduced sequence-based route recognition under substantial appearance change and received the ICRA 2012 Best Robot Vision Paper award. An earlier version had been rejected from ICCV 2011. [S1][S5][S2][S6]

The original SeqSLAM paper introduced sequence-based route recognition under substantial appearance change and received the ICRA 2012 Best Robot Vision Paper award.

2012Experiments
Alderley day–night dataset

The same suburban route was recorded in daylight and during a rainy night. The dataset provides image frames and manually established correspondences for evaluating recognition across changes in illumination and weather. [S2]

The same suburban route was recorded in daylight and during a rainy night.

2012Extensions
Low-resolution route recognition at RSS 2012

Experiments varied image resolution, field of view, bit depth and sequence length. Reported results included recognition with four-pixel images and indoor localisation using two single-pixel light sensors. [S3]

Experiments varied image resolution, field of view, bit depth and sequence length.

2013Extensions
Low-fidelity place recognition in IJRR

The journal study examined seven datasets, varying resolution, pixel depth, field of view, compression, motion blur and sequence length. It also documented failures caused by viewpoint variation and sequence aliasing. [S7]

The journal study examined seven datasets, varying resolution, pixel depth, field of view, compression, motion blur and sequence length.

2013Extensions
Long-exposure localisation

The ICRA 2013 study evaluated localisation with low-cost cameras in dark environments. Experiments included exposures up to 10 seconds from a moving vehicle, substantial motion blur and matching between daytime and night-time imagery. [S8]

The ICRA 2013 study evaluated localisation with low-cost cameras in dark environments.

2013Open source
OpenSeqSLAM and Nordland

An open MATLAB implementation and evaluation on four-season Nordland railway recordings supported reproducible experiments in appearance change. [S9][S10]

An open MATLAB implementation and evaluation on four-season Nordland railway recordings supported reproducible experiments in appearance change.

2013–2014Extensions
SMART: variable-speed route matching

SMART combines whole-image matching with odometry to align observations across traversals with different vehicle speeds, including stops. It appeared at ACRA 2013 and ICRA 2014. [S11][S12]

SMART combines whole-image matching with odometry to align observations across traversals with different vehicle speeds, including stops.

2015Extensions
Predicted depth and event-based sensing

Sequence matching was evaluated with depth predicted by deep learning to address condition and viewpoint change. Separate exploratory work examined event-camera recognition and a neural implementation of SeqSLAM. [S13][S14]

Sequence matching was evaluated with depth predicted by deep learning to address condition and viewpoint change.

2016Extensions
Routed Roads: branching route networks

A directed graph represents image sequences and intersections. A particle filter searches possible paths and image scalings, supporting branching routes and lateral viewpoint changes. [S15]

A directed graph represents image sequences and intersections.

2016Extensions
Intra-image matching for surface registration

Intra-image SeqSLAM matches sequences of patches within images. The ACRA 2016 study evaluated multimodal rock-image registration and laboratory robot-arm positioning under changing illumination, motivated by Mars 2020 targeting requirements. [S30]

Intra-image SeqSLAM matches sequences of patches within images.

2017Extensions
Adaptive sequence length

The temporal window is selected from the statistical significance of candidate localisation hypotheses. Tests with visual and Wi-Fi observations, including reordered traversals, reduced the maximum interval without correct localisation relative to fixed windows while retaining competitive accuracy. [S29]

The temporal window is selected from the statistical significance of candidate localisation hypotheses.

2018Open source
OpenSeqSLAM2.0

The IROS 2018 MATLAB toolbox provides parameter configuration, image-processing and difference-matrix inspection, matched-sequence visualisation, precision–recall analysis and batch parameter sweeps. [S19][S20][S21]

The IROS 2018 MATLAB toolbox provides parameter configuration, image-processing and difference-matrix inspection, matched-sequence visualisation, precision–recall analysis and batch parameter sweeps.

2020Extensions
ConvSequential-SLAM and DeepSeqSLAM

ConvSequential-SLAM combines temporal matching and normalisation with regional image matching. DeepSeqSLAM uses a trainable CNN and recurrent network for joint visual and positional representation learning. [S22][S23]

ConvSequential-SLAM combines temporal matching and normalisation with regional image matching.

2021Extensions
Sequential Place Learning

This preprint develops joint visual and positional learning with a CNN and LSTM, aiming to replace an all-pairs matching matrix and handcrafted temporal filtering with learned inference. [S24]

This preprint develops joint visual and positional learning with a CNN and LSTM, aiming to replace an all-pairs matching matrix and handcrafted temporal filtering with learned inference.

2025Related systems
Neuromorphic place recognition

LENS integrates an event sensor, spiking neural networks and neuromorphic processing for on-device localisation. It represents subsequent work on resource-efficient visual recognition rather than a version of SeqSLAM. [S26]

LENS integrates an event sensor, spiking neural networks and neuromorphic processing for on-device localisation.

08 / Limitations

Scope and limitations

Constraints on visual distinctiveness, viewpoint and motion.

Viewpoint change

Large viewpoint changes can reduce whole-image similarity. Subsequent methods address this through image scaling, predicted depth or regional matching. [S15][S13][S22]

Sequence length

Longer sequences may resolve ambiguity but increase latency and sensitivity to speed changes, junctions and sequence aliasing. [S7][S3]

Evaluation conditions

Performance depends on viewpoint, route ordering, frame spacing, matching tolerance and algorithm parameters. OpenSeqSLAM2.0 supports systematic parameter evaluation. [S9][S11][S19]

09 / Resources

Papers, code and datasets

The original research and practical starting points.

10 / References

References

Sources for the methods, experiments and research connections.

  1. S1 · Michael J. Milford; Gordon F. Wyeth · 2012SeqSLAM: Visual route-based navigation for sunny summer days and stormy winter nights. ICRA, pp. 1643–1649 DOI: 10.1109/ICRA.2012.6224623.
  2. S2 · QUT Centre for Robotics · Project resourceAlderley Day and Night dataset.
  3. S3 · Michael Milford · 2012Visual Route Recognition with a Handful of Bits. Robotics: Science and Systems DOI: 10.15607/RSS.2012.VIII.038.
  4. S4 · OpenSLAM / Niko Sünderhauf · Project resourceOpenSeqSLAM algorithm description.
  5. S5 · Michael Milford · Project resourceSuccess and Rejection Rates in Academia – An Informal, Personal Account.
  6. S6 · IEEE Robotics and Automation Society · 2012ICRA 2012 Awards Ceremony booklet.
  7. S7 · Michael Milford · 2013Vision-based place recognition: how low can you go?. IJRR 32(7), 766–789 DOI: 10.1177/0278364913490323.
  8. S8 · Michael Milford; Ian Turner; Peter Corke · 2013Long Exposure Localization in Darkness Using Consumer Cameras. ICRA2013 paper; archived April 2025
  9. S9 · Niko Sünderhauf; Peer Neubert; Peter Protzel · 2013Are We There Yet? Challenging SeqSLAM on a 3000 km Journey Across All Four Seasons. ICRA Workshop on Long-Term Autonomy
  10. S10 · Niko Sünderhauf / OpenSLAM · 2013OpenSeqSLAM source repository.
  11. S11 · Edward Pepperell; Peter Corke; Michael Milford · 2013Towards Persistent Visual Navigation using SMART. ACRA
  12. S12 · Edward Pepperell; Peter Corke; Michael Milford · 2014All-environment visual place recognition with SMART. ICRA, pp. 1612–1618 DOI: 10.1109/ICRA.2014.6907067.
  13. S13 · Michael Milford; Chunhua Shen; Stephanie Lowry; Niko Sünderhauf; Sareh Shirazi; Guosheng Lin; Fayao Liu; Edward Pepperell; Cesar Lerma; Ben Upcroft; Ian Reid · 2015Sequence Searching With Deep-Learnt Depth for Condition- and Viewpoint-Invariant Route-Based Place Recognition. CVPR Workshops, pp. 18–25
  14. S14 · Michael Milford; Hanme Kim; Michael Mangan; Stefan Leutenegger; Tom Stone; Barbara Webb; Andrew Davison · 2015Place Recognition with Event-based Cameras and a Neural Implementation of SeqSLAM.
  15. S15 · Edward Pepperell; Peter Corke; Michael Milford · 2016Routed roads: Probabilistic vision-based place recognition for changing conditions, split streets and varied viewpoints. IJRR 35(9) DOI: 10.1177/0278364915618766.
  16. S16 · Sayem Mohammad Siam; Hong Zhang · 2017Fast-SeqSLAM: A Fast Appearance Based Place Recognition Algorithm. ICRA, pp. 5702–5708 DOI: 10.1109/ICRA.2017.7989671.
  17. S17 · Project contributors · Project resourceFast-SeqSLAM source code.
  18. S18 · Dongdong Bai; Chaoqun Wang; Bo Zhang; Xiaodong Yi; Xuejun Yang · 2017CNN Feature boosted SeqSLAM for Real-Time Loop Closure Detection.
  19. S19 · Ben Talbot; Sourav Garg; Michael Milford · 2018OpenSeqSLAM2.0: An Open Source Toolbox for Visual Place Recognition Under Changing Conditions. IROS, pp. 7758–7765 DOI: 10.1109/IROS.2018.8593761.
  20. S20 · Michael Milford / QUT · 2018OpenSeqSLAM 2.0 project page.
  21. S21 · Project contributors · Project resourceOpenSeqSLAM2 official QCR repository.
  22. S22 · Mihnea-Alexandru Tomită; Mubariz Zaffar; Michael Milford; Klaus McDonald-Maier; Shoaib Ehsan · 2020ConvSequential-SLAM: A Sequence-based, Training-less Visual Place Recognition Technique for Changing Environments.
  23. S23 · Marvin Chancán; Michael Milford · 2020DeepSeqSLAM: A Trainable CNN+RNN for Joint Global Description and Sequence-based Place Recognition. NeurIPS Workshop on Machine Learning for Autonomous Driving
  24. S24 · Marvin Chancán; Michael Milford · 2021Sequential Place Learning: Heuristic-Free High-Performance Long-Term Place Recognition. arXiv preprint
  25. S25 · Konstantinos A. Tsintotas; Loukas Bampis; Antonios Gasteratos · 2021Tracking-DOSeqSLAM: A dynamic sequence-based visual place recognition paradigm. IET Computer Vision DOI: 10.1049/cvi2.12041.
  26. S26 · Adam D. Hines; Michael Milford; Tobias Fischer · 2025A compact neuromorphic system for ultra-energy-efficient, on-device robot localization. Science Robotics 10(103) DOI: 10.1126/scirobotics.ads3968.
  27. S27 · Michael Milford · 2025The Great Tape Prank. Retrospective personal account; publication date is not the date of the lab incident.
  28. S29 · Jake Bruce; Adam Jacobson; Michael Milford · 2017Look No Further: Adapting the Localization Sensory Window to the Temporal Characteristics of the Environment. IEEE Robotics and Automation Letters 2(4), 2209–2216 DOI: 10.1109/LRA.2017.2724146.
  29. S30 · James Sergeant; Gary Doran; David R. Thompson; Abigail Allwood; Chris Lehnert; Ben Upcroft; Michael Milford · 2016Towards Multimodal and Condition-Invariant Vision-based Registration for Robot Positioning on Changing Surfaces. Australasian Conference on Robotics and Automation (ACRA)
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