Michael Milford / RatSLAM
Robot navigation · Research overview

RatSLAM

Biologically inspired simultaneous localisation and mapping

History, methods and experimental results of a biologically inspired SLAM system.

Conceptual illustration connecting a rat’s spatial memory, a camera-equipped mobile robot and a Brisbane neighbourhood
Conceptual illustration
2003The first RatSLAM paper
66 kmSingle-camera suburb mapping
1,143Office delivery tasks

RatSLAM is a biologically inspired system for simultaneous localisation and mapping. It combines visual recognition, movement estimates and a continuous attractor network with an experience map for navigation. Developed initially at the University of Queensland, it has been evaluated in indoor, suburban and aerial settings and extended through open implementations and multisensor research. [R1][R3][R7][R9][R12][R13]

01 / Experiments

Mapping and navigation experiments

Selected evaluations of map construction and persistent navigation.

St Lucia map comparison from Michael Milford’s research presentation. Historical map data; labels retained.
St Lucia, Brisbane · 2007 data / 2008 paper

Single-camera suburban mapping

A 66 km drive through St Lucia produced a semimetric experience map from a single camera. More than 51 loop closures were detected, including loops up to 5 km long. [R7]

Photo: Michael Milford, reproduced from IEEE Spectrum.
Persistent navigation · 2009–2010

Persistent office navigation

An office robot completed 1,143 delivery tasks to 11 destinations over two weeks. It travelled more than 40 km during 37 active hours and recharged autonomously 23 times. RatSLAM operated with separate navigation and task-selection modules. [R9]

Historical image from Michael Milford’s research presentation; the St Lucia experiment.
St Lucia sensor configuration

Laptop camera input

The St Lucia dataset used the camera built into a laptop mounted on a car. A single image stream supplied visual motion estimates and place recognition. [R7][R17]

02 / Interactive model

Loop-closure demonstration

A synthetic example of accumulated motion error and map correction.

Interactive explanation

Loop closure and map correction

Adjust motion error, route progress and loop-closure correction. Dots represent linked experiences. Synthetic teaching model; the experimental results are shown above.

Preset
Use the controls and the text readout to explore loop closure.
True routeMotion estimateAdjusted map

Here, error is redistributed uniformly once the last 5% of the loop is reached. Real RatSLAM uses learned view associations, attractor dynamics and iterative experience-map relaxation.

03 / Method

RatSLAM architecture

Local-view templates, pose-cell dynamics and an experience map.

Three interacting RatSLAM components: visual templates, a pose-cell attractor network, and an experience graphLocal viewsStored visual templatesPose cellsPosition and headingExperience mapSpatial connectivityPath integration and visual input update pose cells; experience mapping estimates connectivity.
A schematic of the mature RatSLAM architecture. [R4][R13]

Local-view memory

Sensor observations are matched against stored templates. Recognised views activate associated pose states; unfamiliar views can recruit new templates. Similar-looking places can produce ambiguous matches. [R3]

Pose cells

A continuous attractor network represents position and heading. Motion estimates shift its activity, while recognised views inject activity at learned locations. Network dynamics combine these signals over time. [R4]

Experience map

A graph links experiences defined by sensory views and pose states. Estimated movement constrains the links. Loop closures trigger graph adjustment to reduce accumulated error. The map supports navigation independently of the neural coordinates. [R4][R5]

04 / Neuroscience

Biological foundations and computational models

Models of spatial and directional representations used in navigation.

1971

Place cells

The 1971 discovery of hippocampal neurons with location-dependent activity established a foundation for neural spatial representations. This research provided part of RatSLAM’s biological motivation. [R24]

1984–1990

Head-direction cells

Head-direction cells encode heading in an environmental reference frame. Discovered in 1984 and characterised quantitatively in 1990, they complemented place-cell representations in early models of position and orientation. [R25][R26]

2005

Grid cells

Grid cells have spatial firing fields arranged in a triangular lattice. Their discovery, published online in June 2005, followed the initial RatSLAM architecture. Later work examined connections between grid-cell models and computational pose representations. [R27][R1][R2][R11]

Published RatSLAM continuous attractor model with sensory activity injection and path integration.
RatSLAM’s computational model. Figure 1, Milford, Wiles & Wyeth (2010), PLOS Computational Biology. © the authors, Creative Commons Attribution. [R11]
Model results, not animal recordings. Milford, Wiles & Wyeth (2010), PLOS Computational Biology, Figure 4. Source · CC BY.
RatSLAM and neuroscience · 2010

Spatial and directional firing patterns

The 2010 computational study examined spatial firing fields, autocorrelations and directional tuning in the RatSLAM model. [R11]

05 / Development timeline

Development timeline

The original RatSLAM programme, its experiments and collaborative extensions.

17 milestones shown

2003Origins
Initial architecture

The first RatSLAM paper, presented at ACRA 2003, used separate competitive attractor networks for place and head direction. Visual observations recalibrated movement estimates, enabling one-dimensional mapping and self-calibration. Ambiguous two-dimensional environments exposed difficulties in preserving consistent combinations of position and heading. [R1]

The first RatSLAM paper, presented at ACRA 2003, used separate competitive attractor networks for place and head direction.

2004Foundations
Pose cells and natural-scene recognition

ICRA 2004 introduced pose cells: a joint representation of position and heading that addressed the earlier binding problem. Those experiments used artificial landmarks. Later that year, ACRA experiments demonstrated natural-scene recognition in unmodified indoor environments, including a corridor loop and an office floor. [R2][R3]

ICRA 2004 introduced pose cells: a joint representation of position and heading that addressed the earlier binding problem.

2005Foundations
Goal-directed navigation

A goal-memory component learned travel times between place representations during exploration. Following the resulting temporal gradient guided a Pioneer robot towards designated destinations in an office and laboratory. The ICRA 2005 experiments combined real-time SLAM with immediate goal-directed navigation. [R35]

A goal-memory component learned travel times between place representations during exploration.

2005–2006Foundations
Experience mapping

ACRA 2005 introduced an experience graph combining pose, view and movement information. Graph adjustment produced a spatially coherent map despite discontinuities in the neural representation. IROS 2006 evaluated limited pose-cell resources, goal-directed navigation and adaptation to simple environmental changes. [R4][R5]

ACRA 2005 introduced an experience graph combining pose, view and movement information.

2005–2006Experiments
Outdoor mapping

Outdoor experiments extended RatSLAM to less controlled visual conditions and robot motion. The work appeared in the Field and Service Robotics research cycle and as a 2006 Springer chapter, preceding the larger suburban mapping experiments. [R6]

Outdoor experiments extended RatSLAM to less controlled visual conditions and robot motion.

2007Extensions
RatChat spatial concepts

RatChat associated RatSLAM experience representations with concepts such as rooms and corridors. A single-layer neural network learned these associations through a teacher–student process and recognised them on revisits. The experiments ran offline on representations obtained during Pioneer robot exploration. [R36]

RatChat associated RatSLAM experience representations with concepts such as rooms and corridors.

2008Experiments
Single-camera suburban mapping

A 66 km drive through St Lucia, Brisbane, supplied webcam images at 10 Hz over approximately 100 minutes. Visual motion estimation and place recognition produced a coherent semimetric road map with more than 51 loop closures, including loops up to 5 km long. Data were collected in 2007; the journal paper appeared in 2008. [R7][R17]

A 66 km drive through St Lucia, Brisbane, supplied webcam images at 10 Hz over approximately 100 minutes.

2008Foundations
Robot Navigation from Nature

The 2008 book consolidated the neuroscience motivation, computational architecture and navigation experiments. Published as volume 41 of Springer Tracts in Advanced Robotics, it covers simultaneous localisation, mapping and path planning based on hippocampal models. [R8]

The 2008 book consolidated the neuroscience motivation, computational architecture and navigation experiments.

2009–2010Experiments
Persistent office navigation

Over two weeks, an office robot completed 1,143 delivery tasks to 11 destinations, with one delivery failure and subsequent recovery. It travelled more than 40 km during 37 active hours and recharged autonomously 23 times. SLAM operated alongside navigation and task-selection modules. The study appeared online in 2009 and in the 2010 IJRR volume. [R9]

Over two weeks, an office robot completed 1,143 delivery tasks to 11 destinations, with one delivery failure and subsequent recovery.

2009–2010Extensions
FAB-MAP integration

FAB-MAP + RatSLAM combined probabilistic appearance recognition with pose filtering and experience mapping. The ICRA 2010 study evaluated observations collected at different times of day, integrating an independently developed recognition method with the RatSLAM architecture. [R10]

FAB-MAP + RatSLAM combined probabilistic appearance recognition with pose filtering and experience mapping.

2010Neuroscience
Grid-cell models and navigational uncertainty

RatSLAM maintained competing pose hypotheses in ambiguous environments until sequences of observations distinguished them. The 2010 computational neuroscience study proposed that conjunctive grid-like cells could filter uncertain sensory information. This was a computational hypothesis evaluated through modelling and robotic navigation. [R11]

RatSLAM maintained competing pose hypotheses in ambiguous environments until sequences of observations distinguished them.

2011Experiments
Aerial SLAM with visual expectation

ICRA 2011 experiments used imagery from a micro aerial vehicle. Visual odometry and place recognition from approximately 1,000-pixel images were combined with anticipated image sequences to improve recall and precision. Outdoor observations included low-quality and intermittent visual input. [R12]

ICRA 2011 experiments used imagery from a micro aerial vehicle.

2011Extensions
Mapping in 2.5D

A 2011 study integrated multicamera visual odometry with RatSLAM on a 1,300 m dataset. Altitude was added to experience-map nodes and altitude changes to links, while pose cells retained the x, y and heading representation. This extended the map to 2.5D without increasing the pose network’s dimensionality. [R28]

A 2011 study integrated multicamera visual odometry with RatSLAM on a 1,300 m dataset.

2012Related systems
SeqSLAM route recognition

SeqSLAM uses sequences of images for route recognition under substantial appearance change. It is a distinct method from RatSLAM and does not include pose-cell dynamics or experience mapping. [R34][R4]

SeqSLAM uses sequences of images for route recognition under substantial appearance change.

2013Open source
OpenRatSLAM

The 2013 open implementation separated local-view processing, pose cells and experience mapping into ROS components, with a separate visual-odometry node. The publication documented interfaces, parameters and tuning, and provided demonstrations on three public datasets. [R13]

The 2013 open implementation separated local-view processing, pose cells and experience mapping into ROS components, with a separate visual-odometry node.

2014–2015Extensions
Autonomous multisensor calibration

Movement-based calibration estimated self-motion and place-recognition parameters, while online weighting adapted sensor contributions. Tests used several robot and sensor configurations in offices, a university campus and a forest, producing topologically correct maps in most tested conditions. The study appeared online in 2014 and in the 2015 journal volume. [R14]

Movement-based calibration estimated self-motion and place-recognition parameters, while online weighting adapted sensor contributions.

2019Related systems
NeuroSLAM

NeuroSLAM combines three-dimensional grid-cell models and layered head-direction representations in a four-degree-of-freedom architecture. Its multilayered experience map is adjusted after loop closure. Evaluation used synthetic and real indoor and outdoor datasets. Lead researcher Fangwen Yu visited Milford’s lab during this research. [R16]

NeuroSLAM combines three-dimensional grid-cell models and layered head-direction representations in a four-degree-of-freedom architecture.

07 / Limitations

Scope and limitations

Representation, sensing and implementation constraints.

Biological scope

RatSLAM models selected mechanisms of sensory recognition, movement integration and spatial memory. The grid-cell study proposed a computational role in uncertainty resolution, rather than a complete account of biological navigation. [R11]

Map representation

The experience map represents connectivity and approximate geometry. Dense reconstruction, obstacle avoidance and survey-grade positioning require additional capabilities. The delivery experiments used separate planning and control components. [R7][R9]

Perceptual ambiguity

Repeated textures, appearance changes and viewpoint variation can impair template matching. Multimodal sensing and learned representations address some of these limitations in later extensions. [R15][R18]

Evaluation conditions

Performance depends on network size, recognition thresholds, sensors, software and test conditions. Results are specific to the implementation and evaluation dataset. [R13][R19][R22]

08 / Resources

Papers, code and demonstrations

The original research and software.

09 / References

References

Sources for the research, experiments and follow-on work.

  1. R1 · Michael Milford; Gordon Wyeth · 2003Hippocampal Models for Simultaneous Localisation and Mapping on an Autonomous Robot. ACRA 2003
  2. R2 · Michael Milford; Gordon Wyeth; David Prasser · 2004RatSLAM: a hippocampal model for simultaneous localization and mapping. ICRA 2004, 403–408 DOI: 10.1109/ROBOT.2004.1307183.
  3. R3 · Michael Milford; Gordon Wyeth; David Prasser · 2004Simultaneous Localisation and Mapping from Natural Landmarks using RatSLAM. ACRA 2004
  4. R4 · Michael Milford; David Prasser; Gordon Wyeth · 2005Experience Mapping: Producing Spatially Continuous Environment Representations using RatSLAM. ACRA 2005
  5. R5 · Michael Milford; Gordon Wyeth; David Prasser · 2006RatSLAM on the Edge: Revealing a Coherent Representation from an Overloaded Rat Brain. IROS 2006, 4060–4065 DOI: 10.1109/IROS.2006.281869.
  6. R6 · David Prasser; Michael Milford; Gordon Wyeth · 2006Outdoor Simultaneous Localisation and Mapping Using RatSLAM. Field and Service Robotics, Springer Tracts in Advanced Robotics 25 DOI: 10.1007/978-3-540-33453-8_13.
  7. R7 · Michael J. Milford; Gordon F. Wyeth · 2008Mapping a Suburb With a Single Camera Using a Biologically Inspired SLAM System. IEEE Transactions on Robotics 24(5), 1038–1053 DOI: 10.1109/TRO.2008.2004520.
  8. R8 · Michael John Milford · 2008Robot Navigation from Nature: Simultaneous Localisation, Mapping, and Path Planning Based on Hippocampal Models. Springer Tracts in Advanced Robotics 41 DOI: 10.1007/978-3-540-77520-1.
  9. R9 · Michael Milford; Gordon Wyeth · 2010Persistent Navigation and Mapping using a Biologically Inspired SLAM System. International Journal of Robotics Research 29(9), 1131–1153; online 21 July 2009 DOI: 10.1177/0278364909340592.
  10. R10 · Arren Glover; William Maddern; Michael Milford; Gordon Wyeth · 2010FAB-MAP + RatSLAM: Appearance-based SLAM for multiple times of day. ICRA 2010, 3507–3512 DOI: 10.1109/ROBOT.2010.5509547.
  11. R11 · Michael J. Milford; Janet Wiles; Gordon F. Wyeth · 2010Solving Navigational Uncertainty Using Grid Cells on Robots. PLOS Computational Biology 6(11), e1000995 DOI: 10.1371/journal.pcbi.1000995.
  12. R12 · Michael J. Milford; Felix Schill; Peter Corke; Robert Mahony; Gordon Wyeth · 2011Aerial SLAM with a single camera using visual expectation. ICRA 2011, 2506–2512 DOI: 10.1109/ICRA.2011.5980329.
  13. R13 · David Ball; Scott Heath; Janet Wiles; Gordon Wyeth; Peter Corke; Michael Milford · 2013OpenRatSLAM: an open source brain-based SLAM system. Autonomous Robots 34, 149–176 DOI: 10.1007/s10514-012-9317-9.
  14. R14 · Adam Jacobson; Zetao Chen; Michael Milford · 2015Autonomous Multisensor Calibration and Closed-loop Fusion for SLAM. Journal of Field Robotics 32(1), 85–122; online February 2014 DOI: 10.1002/rob.21500.
  15. R15 · Oliver Struckmeier; Kshitij Tiwari; Mohammed Salman; Martin J. Pearson; Ville Kyrki · 2019ViTa-SLAM: A Bio-inspired Visuo-Tactile SLAM for Navigation while Interacting with Aliased Environments. IEEE Cyborg and Bionic Systems 2019
  16. R16 · Fangwen Yu et al. · 2019NeuroSLAM: a brain-inspired SLAM system for 3D environments. Biological Cybernetics 113, 515–545 DOI: 10.1007/s00422-019-00806-9.
  17. R17 · davidmball/ratslam contributors · Project resourceOpenRatSLAM project repository. ROS branch and separate C++ library; lists iRat 2011, St Lucia 2007 and Oxford New College 2008 datasets.
  18. R18 · Ozan Çatal; Wouter Jansen; Tim Verbelen; Bart Dhoedt; Jan Steckel · 2021LatentSLAM: unsupervised multi-sensor representation learning for localization and mapping. ICRA 2021
  19. R19 · Mauro Enrique de Souza Muñoz; Matheus Chaves Menezes; Edison Pignaton de Freitas; Sen Cheng; Paulo Rogério de Almeida Ribeiro; Areolino de Almeida Neto; Alexandre César Muniz de Oliveira · 2022xRatSLAM: An Extensible RatSLAM Computational Framework. Sensors 22(21), 8305 DOI: 10.3390/s22218305.
  20. R20 · Matheus Menezes; Mauro Muñoz; Edison Pignaton de Freitas; Sen Cheng; Areolino de Almeida Neto; Paulo Ribeiro; Alexandre Oliveira · 2023A Multisession SLAM Approach for RatSLAM. Journal of Intelligent & Robotic Systems 108, article 61 DOI: 10.1007/s10846-023-01816-3.
  21. R21 · Carlos Alexandre Pontes Pizzino; Ramon Romankevicius Costa; Daniel Mitchell; Patrícia Amâncio Vargas · 2024NeoSLAM: Long-Term SLAM Using Computational Models of the Brain. Sensors 24(4), 1143 DOI: 10.3390/s24041143.
  22. R22 · Joao Victor T. Borges; Fabio Coelho; Paulo Padrao; Jose Fuentes; Ramon R. Costa; Liu Hsu; Leonardo Bobadilla · 2026A New Implementation of NeoSLAM and a Comparative Evaluation with RatSLAM. arXiv preprint, submitted 17 July 2026 DOI: 10.48550/arXiv.2607.16143.
  23. R23 · Fabio Coelho; Joao Victor T. Borges; Paulo Padrao; Jose Fuentes; Ramon R. Costa; Liu Hsu; Leonardo Bobadilla · 2025Bioinspired SLAM Approach for Unmanned Surface Vehicle. arXiv preprint, submitted 23 September 2025 DOI: 10.48550/arXiv.2509.19522.
  24. R24 · John O’Keefe; Jonathan Dostrovsky · 1971The hippocampus as a spatial map. Preliminary evidence from unit activity in the freely-moving rat. Brain Research 34(1), 171–175 DOI: 10.1016/0006-8993(71)90358-1.
  25. R25 · Jeffrey S. Taube; Robert U. Muller; James B. Ranck Jr. · 1990Head-direction cells recorded from the postsubiculum in freely moving rats. I. Description and quantitative analysis. Journal of Neuroscience 10(2), 420–435 DOI: 10.1523/JNEUROSCI.10-02-00420.1990.
  26. R26 · Jeffrey S. Taube · 2025The Discovery of Head Direction Cells: A Personal Account. Hippocampus; firsthand retrospective, online 2024 / issue 2025 DOI: 10.1002/hipo.23670.
  27. R27 · Torkel Hafting; Marianne Fyhn; Sturla Molden; May-Britt Moser; Edvard I. Moser · 2005Microstructure of a spatial map in the entorhinal cortex. Nature 436, 801–806; online 19 June 2005, issue 11 August 2005 DOI: 10.1038/nature03721.
  28. R28 · Michael Milford; David McKinnon; Michael Warren; Gordon Wyeth; Ben Upcroft · 2011Feature-based Visual Odometry and Featureless Place Recognition for SLAM in 2.5D Environments. ACRA 2011
  29. R29 · Jan Steckel; Herbert Peremans · 2013BatSLAM: Simultaneous Localization and Mapping Using Biomimetic Sonar. PLOS ONE 8(1), e54076; 24 January 2013 DOI: 10.1371/journal.pone.0054076.
  30. R30 · Mohammed A. T. S. Salman; Martin Pearson · 2016Advancing whisker based navigation through the implementation of Bio-Inspired whisking strategies. ROBIO 2016; online publication 2 March 2017 DOI: 10.1109/ROBIO.2016.7866416.
  31. R31 · Mohammed Salman; Martin J. Pearson · 2018Whisker-RatSLAM Applied to 6D Object Identification and Spatial Localisation. Living Machines 2018, LNCS 10928, 403–414 DOI: 10.1007/978-3-319-95972-6_44.
  32. R32 · Martin J. Pearson; Charles Fox; J. Charles Sullivan; Tony J. Prescott; Tony Pipe; Ben Mitchinson · 2013Simultaneous localisation and mapping on a multi-degree of freedom biomimetic whiskered robot. ICRA 2013, 586–592 DOI: 10.1109/ICRA.2013.6630633.
  33. R34 · Michael J. Milford; Gordon F. Wyeth · 2012SeqSLAM: Visual route-based navigation for sunny summer days and stormy winter nights. ICRA 2012 DOI: 10.1109/ICRA.2012.6224623.
  34. R35 · Michael Milford; Gordon Wyeth; David Prasser · 2005Efficient Goal Directed Navigation using RatSLAM. ICRA 2005, 1097–1102 DOI: 10.1109/ROBOT.2005.1570262.
  35. R36 · Michael Milford; Ruth Schulz; David Prasser; Gordon Wyeth; Janet Wiles · 2007Learning spatial concepts from RatSLAM representations. Robotics and Autonomous Systems 55(5), 403–410 DOI: 10.1016/j.robot.2006.12.006.
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