# Experimental Evaluation of a UWB-Based Cooperative Positioning System for Pedestrians in GNSS-Denied Environment

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## Abstract

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## 1. Introduction

## 2. State-of-the-Art in UWB Positioning

#### 2.1. TOA, RTT, and TDOA-Based Methods

#### 2.2. AOA-Based Methods

#### 2.3. RSSI-Based Methods

#### 2.4. Hybrid Methods

## 3. CP Prototype System and Experiences

#### 3.1. MUPS Prototype

#### UWB Systems Description

#### 3.2. Description of Field Test Site

#### 3.3. Data Collection Procedure

#### 3.4. Data Availability in Different Environments

## 4. Positioning Framework

## 5. Results and Discussion

^{−2}. The parameters of EKF (such as Q and R) should be determined using a Kalman Filter tuning procedure. However, tuning a centralised EKF can be quite challenging. Therefore, these parameters were determined using a trial and error method. As detailed in Section 3.3, ground truth checkpoints were used to test MUPS performance in the indoor environment.

#### 5.1. User Z: P2I vs. P2P+P2I

#### 5.2. User C: P2I vs. P2P+P2I

## 6. Conclusions

## Author Contributions

## Funding

## Conflicts of Interest

## References

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**Figure 1.**One of the MUPS prototypes with sensors, including a compact GNSS receiver, UWB radios, and a smartphone.

**Figure 3.**Sketch of the test site showing the locations of all the anchors. The numbers such as 106, 6809, and $682d$ represent the unique UWB identifiers.

**Figure 4.**Scaled plot of the test environment with anchor UWBs and ground truth checkpoints. The numbers, such as 106, 6809, and 682d, represent the unique UWB identifiers.

**Figure 5.**Environment transitions. O indicates the outdoor area, S indicates the staircase area, and I indicates the indoor area.

**Figure 7.**Number of available measurements from User Z to Time Domain UWB anchors. O1–O4, I1–I4, and S1–S7 denote time instants when the user was outdoors, indoors (hallway), and on the staircase, respectively.

**Figure 8.**Number of available measurements from User C to Pozyx UWB anchors. O1–O3, I1–I2, and S1–S4 denote time instants when the user was outdoors, indoors (hallway), and on the staircase, respectively.

**Figure 9.**Estimated positions of the User Z for trajectory S1–I1–S2. Positions are estimated using Time Domain UWB data only (P2I EKF).

**Figure 10.**Estimated positions of the User Z for trajectory S1–I1–S2. Positions are estimated using Time Domain UWB and User C’s data (P2P+P2I EKF).

**Figure 11.**Comparison of estimated errors at each checkpoint with respective values of HDOP (upper graph) and the number of available measurements (bottom graph) for trajectory S1–I1–S2 for User Z. Positions were estimated using Time Domain UWB data only (P2I EKF).

**Figure 12.**Comparison of estimated errors at each checkpoint with respective values of HDOP (upper graph) and the number of available measurements (bottom graph) for trajectory S1–I1–S2 for User Z. Positions were estimated using Time Domain UWB and User C’s data (P2P+P2I EKF).

**Figure 13.**Comparison of RMSE values for P2I and P2P+P2I, for User Z. If improvement is observed, the line is oriented upwards (i.e., value of RMSE is reduced).

**Figure 14.**Estimated positions of the User C for trajectory S1–I1–S2. Positions are estimated using Pozyx UWB data only (P2I EKF). The graph on the right shows the zoomed view of the estimated positions.

**Figure 15.**Estimated positions of the User C for trajectory S1–I1–S2. Positions are estimated using Pozyx UWB data and User Z’s data (P2P+P2I EKF).

**Figure 16.**Comparison of estimated errors at each checkpoint with respective values of HDOP (upper graph) and the number of available measurements (bottom graph) for trajectory S1–I1–S2 for User C. Positions are estimated using Pozyx UWB data only (P2I EKF).

**Figure 17.**Comparison of estimated errors at each checkpoint with respective values of HDOP (upper graph) and the number of available measurements (bottom graph) for trajectory S1–I1–S2 for User C. Positions are estimated using Pozyx UWB and User Z’s data (P2P+P2I EKF).

**Figure 18.**Comparison of RMSE values for P2I and P2P+P2I, for User C. If improvement is observed, the line is oriented upwards (i.e., value of RMSE is reduced).

Item | Time Domain | Pozyx |
---|---|---|

Dimensions | $76\times 80$ mm | $71.75\times 58$ mm |

Weight | 58 g | 12 g |

Ranging Accuracy | ∼2–3 cm | ∼10 cm |

Other sensors | - | 9-axes IMU |

Pressure sensor |

User Z | P2I | P2P+P2I | ||||||||
---|---|---|---|---|---|---|---|---|---|---|

Point ID | RMSE | Avg | Max | Avg | Max | RMSE | Avg | Max | Avg | Max |

[m] | [m] | [m] | HDOP | HDOP | [m] | [m] | [m] | HDOP | HDOP | |

UWB 100 | 0.66 | 0.61 | 0.86 | 2.31 | 2.47 | 0.43 | 0.42 | 0.50 | 1.87 | 2.27 |

UWB 206 | 0.62 | 0.62 | 0.71 | 0.92 | 0.92 | 0.65 | 0.64 | 0.78 | 0.86 | 0.87 |

1 | 0.96 | 0.90 | 1.92 | 5.83 | 25.60 | 2.54 | 2.50 | 3.48 | 1.12 | 1.20 |

3 | 0.17 | 0.16 | 0.22 | 2.43 | 2.43 | 0.16 | 0.16 | 0.22 | 2.21 | 2.22 |

30 | 0.13 | 0.12 | 0.24 | 1.99 | 2.00 | 0.47 | 0.40 | 0.87 | 1.97 | 1.98 |

31 | 0.18 | 0.16 | 0.39 | 1.62 | 1.65 | 0.17 | 0.15 | 0.39 | 1.61 | 1.65 |

32 | 0.27 | 0.25 | 0.55 | 1.36 | 1.41 | 0.31 | 0.30 | 0.57 | 1.36 | 1.40 |

33 | 0.16 | 0.15 | 0.20 | 1.95 | 1.96 | 0.16 | 0.16 | 0.21 | 1.93 | 1.94 |

34 | 0.71 | 0.51 | 2.34 | 2.24 | 2.86 | 0.73 | 0.53 | 2.25 | 2.24 | 2.85 |

35 | 1.27 | 1.03 | 3.62 | 4.36 | 11.40 | 1.04 | 0.73 | 3.49 | 4.30 | 11.35 |

36 | 1.71 | 1.63 | 2.74 | 1.12 | 1.22 | 0.90 | 0.77 | 1.61 | 1.09 | 1.17 |

37 | 0.68 | 0.64 | 1.14 | 1.09 | 1.21 | 0.68 | 0.64 | 1.14 | 0.87 | 1.21 |

User C | P2I | P2P+P2I | ||||||||
---|---|---|---|---|---|---|---|---|---|---|

Point ID | RMSE | Avg | Max | Avg | Max | RMSE | Avg | Max | Avg | Max |

[m] | [m] | [m] | HDOP | HDOP | [m] | [m] | [m] | HDOP | HDOP | |

UWB 617d | 0.45 | 0.44 | 0.52 | 1.33 | 1.61 | 0.36 | 0.36 | 0.36 | 1.05 | 1.05 |

UWB 683c | 0.64 | 0.63 | 0.75 | 1.20 | 1.35 | 0.74 | 0.74 | 0.74 | 1.35 | 1.35 |

UWB 686c | 0.61 | 0.52 | 0.84 | 2.23 | 2.89 | 0.41 | 0.34 | 0.57 | 1.57 | 1.57 |

2 | 77.22 | 75.77 | 93.29 | Inf * | Inf | 1.49 | 1.33 | 2.50 | Inf | Inf |

30 | 95.54 | 95.13 | 112.53 | Inf | Inf | 0.99 | 0.83 | 1.76 | Inf | Inf |

31 | 86.52 | 86.29 | 99.78 | Inf | Inf | 3.82 | 2.78 | 8.96 | Inf | Inf |

33 | 48.35 | 48.20 | 54.19 | Inf | Inf | 0.90 | 0.80 | 1.29 | Inf | Inf |

34 | 24.01 | 23.72 | 28.25 | Inf | Inf | 0.95 | 0.75 | 1.55 | Inf | Inf |

35 | 15.09 | 14.38 | 21.22 | Inf | Inf | 0.91 | 0.71 | 1.49 | Inf | Inf |

36 | 7.33 | 6.73 | 12.24 | Inf | Inf | 1.07 | 0.88 | 2.21 | Inf | Inf |

37 | 0.28 | 0.27 | 0.46 | Inf | Inf | 0.80 | 0.70 | 1.67 | Inf | Inf |

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## Share and Cite

**MDPI and ACS Style**

Gabela, J.; Retscher, G.; Goel, S.; Perakis, H.; Masiero, A.; Toth, C.; Gikas, V.; Kealy, A.; Koppányi, Z.; Błaszczak-Bąk, W.;
et al. Experimental Evaluation of a UWB-Based Cooperative Positioning System for Pedestrians in GNSS-Denied Environment. *Sensors* **2019**, *19*, 5274.
https://doi.org/10.3390/s19235274

**AMA Style**

Gabela J, Retscher G, Goel S, Perakis H, Masiero A, Toth C, Gikas V, Kealy A, Koppányi Z, Błaszczak-Bąk W,
et al. Experimental Evaluation of a UWB-Based Cooperative Positioning System for Pedestrians in GNSS-Denied Environment. *Sensors*. 2019; 19(23):5274.
https://doi.org/10.3390/s19235274

**Chicago/Turabian Style**

Gabela, Jelena, Guenther Retscher, Salil Goel, Harris Perakis, Andrea Masiero, Charles Toth, Vassilis Gikas, Allison Kealy, Zoltán Koppányi, Wioleta Błaszczak-Bąk,
and et al. 2019. "Experimental Evaluation of a UWB-Based Cooperative Positioning System for Pedestrians in GNSS-Denied Environment" *Sensors* 19, no. 23: 5274.
https://doi.org/10.3390/s19235274