1. Research Paper: Accurate Real-Time Relative Localization Using Single-Frequency GPS
Researchers: Will Hedgecock, Miklos Maroti, Akos Ledeczi, Peter Volgyesi, and Rueben Banalagay
(Institute for Software Integrated Systems, Vanderbilt University)
Presenter: Bilal Korir

2. A short intro to how the GPS works+

3. A short intro to how the GPS works
Since 1970’s continuously send data to earth over dedicated radio frequencies.
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4. A short intro to how the GPS works
More than 24 satellites orbiting at 12,000 mile height
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5. A short intro to how the GPS works
Sky above you will always contain at most 12 satellites
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6. A short intro to how the GPS works
GPS satellites have atomic clock
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7. A short intro to how the GPS works
4 satellites are required for accurate localization
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8. A short intro to how the GPS works
$GPRMC, ,A, ,N, ,W,0.09,144.75,141112,,*19
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9. A short intro to how the GPS works?
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10. Motivation
low-cost GPS is typically insufficient for use in high-precision applications
The need for relative position.
Smartphones’ GPS can exhibit large errors on the order of tens of meters. especially in challenging RF environments.
Potential use cases need relative localization are, autonomous driving and collision avoidance.

11. Proposal Novel approach to derive relative location
Challenging the beliefs the accurate localization requires stationary calibration time and expensive equipment.
Aims to bridge the gap between low-cost and high accuracy
Achieve an unprecedented decimeter-scale level

12. Existing solutions Differential GPS (DGPS)
Wide-Area Augmentation System (WAAS)
Real-Time Kinematic (RTK)

13. How does it work?

14. RegTrack a High level look

15. RegTrack a Low level look
Double-differenced model: localization Cannot detect cycle slip, satellite must remain visible, receiver- satellite range calculated and compared many times before generating most accurate result, receiver must remain stationary.

16. RegTrack a Low level look
Ambiguity Function Value Method : Minimize the range error in the previews method, immune to cycle slips, choose the best candidate. Pre-supposes all satellite observations to be error-free, cannot be used over time unless both receivers remain stationary.

17. RegTrack a Low level look
AFV Peak Tracking Method: Creating a map, AFV scan the map and chooses the best candidate, one valid peak remaining corresponding to the correct relative baseline between the two receivers.

18. RegTrack a Low level look
Extended AFM with Hill Climbing: Improve tracking especially if the object is moving.

19. RegTrack a Low level look
AFV Thresholding Function: Filter out baseline positions that have become unfit candidates over time.

20. Result
7-33x improvement in good condition environment 2-3x improvement in challenging condition environment Precision on the order of decimeters

21. Personal judgement
The team has done a great job and achieve remarkable result using single-frequency low-cost GPS.

22. Thank you