A Vision-Based Mobile Platform for Seamless Indoor/Outdoor Positioning

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The emergence of smartphones equipped with Internet access, high resolution cameras, and posi- tioning sensors opens up great opportunities for visualising geospatial information within augmented reality applications. While smartphones are able to provide geolocalisation, the inherent uncertainty in the estimated position, especially indoors, does not allow for completely accurate and robust alignment of the data with the camera images.
In this paper we present a system that exploits computer vision techniques in conjunction with GPS and inertial sensors to create a seamless indoor/outdoor positioning vision-based platform. The vision-based approach estimates the pose of the camera relative to the fac ̧ade of a building and recognises the fac ̧ade from a georeferenced image database. This permits the insertion of 3D widgets into the user’s view with a known orientation relative to the fac ̧ade. For example, in Figure 1 (a) we show how this feature can be used to overlay directional information on the input image. Furthermore we provide an easy and intuitive interface for non-expert users to add their own georeferenced content to the system, encouraging volunteering GI. Indeed, to achieve this users only need to drag and drop predefined 3D widgets into a reference view of the fac ̧ade, see Figure 1 (b). The infrastructure is flexible in that we can add different layers of content on top of the fac ̧ades and hence, this opens many possibilities for different applications. Furthermore the system provides a representation suitable for both manual and automatic content authoring.

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A Vision-Based Mobile Platform for Seamless Indoor/Outdoor Positioning

  1. 1. A Vision-Based Mobile Platform for Seamless Indoor/Outdoor Positioning Guillaume GALES Eric MCCLEAN John MCDONALD DEPARTMENT OF COMPUTER SCIENCE NATIONAL UNIVERSITY OF IRELAND MAYNOOTH
  2. 2. Introduction Internet access Accelerometer GPS / Compass Camera 2
  3. 3. Introduction Vision-based platform for positioning Internet access PositionCamera pose 3
  4. 4. IntroductionVision-based platform for positioning Georeferenced façade database Façade recognition system Client applications 4
  5. 5. IntroductionVision-based platform for positioning Client applications 5
  6. 6. Example of AR applicationMobile client side RenderingServer side Façade Widget extraction RetrievalDatabase Authoring client Façade Matching 6
  7. 7. Example of application 7
  8. 8. OutlineVison-based platform• Façade extraction• Georeferenced façade database• Façade recognition system• Camera pose estimationApplications• Augmented reality• Navigation• PositioningConclusion and perspectives 8
  9. 9. Vison-based platform
  10. 10. Façade ExtractionKey of the vision-based platform • Georeferenced façades are the frame of references of 3D contentInput: image of a façadeOutput: homography between the façade and its imageAdvantages: • Robust matching (invariant to rotation and perspective changes) • Façade normalization (used to build a representation of the environment) • Camera pose estimation (used by the visualization system) 10
  11. 11. Façade Extraction 11
  12. 12. Georeferenced façade database For each street, take pictures of façades Automatic façade extraction, matching and stitching • Geometrical constraint makes matching robust • Invariance to rotation and perspective changes 12
  13. 13. Georeferenced façade database 13
  14. 14. Georeferenced façade database 14
  15. 15. Façade recognition systemCandidate selection• GPS coordinates• Bag-of-word description for selecting candidatesSimilarity constraint Figure 2: Database infrastructure for computing planar facade mo- ¸ saics. The individual facades are stitched together into planes to ¸ 15 build a frame of reference for authoring.
  16. 16. Camera pose estimation intrinsics are known extrinsics are given by the façade extraction algorithm (homography between plane and its image decomposed into rotation and translation) 2 3 0 0 sh sh ⇥ ⇤ 60 h h 07x=K R t 640 7 0 0 05 1 1 1 1 0 2 3 0 0 sh sh = H 40 h h 05 H sh 1 1 1 1 h 1 H Façade Camera 16
  17. 17. Applications
  18. 18. Augmented realityExtension of façade to 3D: frame of reference 18
  19. 19. Augmented realityDesktop application• Easy and intuitive interface to use for non expert users• Predefined list of 3D models 19
  20. 20. National University of National University of National University of Ireland Maynooth Ireland Augmented reality Ireland Maynooth Ireland Ireland Maynooth IrelandT horing is an important stage in the workflow of creat-gmented reality applications. In this paper we describesed database infrastructure for authoring and storing 3D use in urban environments. It provides frames of ref- he environment as well as a mechanism to match newh the facades and thus retrieving associated 3D content. ¸ ucture is flexible in that we can add different 3D “lay-tent on top of the facades and hence opens many pos- ¸ Façade Extraction augmented reality applications in urban environments.e the system provides a representation suitable for both Pose Estimation automatic content authoring.ds: Augmented Reality, Infrastructure, Authoring, Façade Matchinged Database, Content Storing and Retrieving.DUCTION Widget Retrieval useful in-mented reality applications provide rich ando their users about their surrounding environment. Toe augmented reality applications, an efficient infrastruc-red. Such infrastructures involve:ng a map of the environment ;g content ;ving content.aper we propose an infrastructure that makes authoringve and flexible. Our goal is to create a platform for mo- 20
  21. 21. Results 21
  22. 22. Navigation Vision-based platform for positioning + Path finding algorithm Outdoor/Indoor navigation application 22
  23. 23. PositioningAccurate positioning (ongoing work) 23
  24. 24. Conclusion and perspectives
  25. 25. Conclusion and perspectivesVision-based platform for positioning• Georeferenced façade database• Façade recognition systemMobile applications• Augmented reality - Authoring solution - User generated content - Collaborative GI (HTML5)• Navigation (Ongoing)• Optimisations 25
  26. 26. AcknowledgmentResearch presented in this paper was funded by a StrategicResearch Cluster grant (07/SRC/I1169) by ScienceFoundation Ireland under the National Development Plan.The authors gratefully acknowledge this support.Thank you for your attention 26

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