Inside GNSS Media & Research

NOV-DEC 2018

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46 InsideGNSS N O V E M B E R / D E C E M B E R 2 0 1 8 www.insidegnss.com BLUEGNSS FIGURE 19 Example of GPS/EGNOS positioning accuracy (from a BLUEGNSS monthly report) February 2018 HPE 95% (m) 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 20 16 12 8 4 0 February 2018 HPE 95% (m) 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 20 16 12 8 4 0 (a) Horizontal accuracy plot with APV-I target (c) Horizontal accuracy plot with LPV-200 target February 2018 VPE 95% (m) 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 30 25 20 15 10 5 0 February 2018 VPE 95% (m) 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 30 25 20 15 10 5 0 (b) Vertical accuracy plot with APV-I target (d) Vertical accuracy plot with LPV-200 target Output typology is similar to the GPS positioning accuracy. Figure 19 shows some examples in which the ICAO APV-I and LPV-200 thresholds are never violated within the month of interest. GPS-EGNOS.KPI-2: Service Availability The percentage of service availability (xSA, where x can be H in the case of horizontal or V in case of vertical) is assessed by computing the following daily probabilities: where H/ V PL i a re respec t ively t he hor i zonta l /ver t ica l protec t ion lev- els at the i-th epoch and H/VAL are respect ively t he horizontal/ver tical aler t limit der ived f rom t he ICAO SARPs, i.e., APV-I: HAL = 40 meters and VAL = 50 meters, LPV-200: HAL = 40 meters and VAL = 35 meters. Figure 20 shows an example of GPS/ EGNOS service availability plots against the ICAO APV-I and LPV-200 thresh- olds. Specifically, all graphs report a service availability level that is always > 99%. GPS-EGNOS.KPI-3: Integrity Integrity Integrity is a measure of the trust that can be placed in the correctness of the information supplied by the total system. Integrity includes the ability of a system to provide timely and valid warnings to the user (alerts) when the system must not be ID Parameter Definition Target Note GPS_EGNOS. KPI-1 Positioning accuracy 95th-percentile of position error, intended as the difference between estimated receiver positions and the reference one, calculated over any interval of 24hrs, for any point within the service volume APV-I LPV ICAO SARPs and ICAO Doc-9849, see Additional Resources HPE 16 m 16 m VPE 20 m 6 ÷ 4 m GPS_EGNOS. KPI-2 Service availability Percentage of epochs in which protection levels are below alert limits for the selected service (APV-I or LPV-200) over the total period APV-I LPV - HSA def.: Pr{HPL i ≤ HAL} - VSA def.: Pr{VPLi ≤ VAL} for all i-epochs belonging to the period of analysis HPE ≥ 99% ≥ 99% VPE ≥ 99% ≥ 99% GPS_EGNOS. KPI-3 Integrity This metric is calculated in terms of integrity events (IE). An IE occurs when the navigation system error is greater or equal to the corresponding protection level for the corresponding service level (e.g. APV-I) and the receiver does not trigger an alert within the time-to-alert (TTA) - APV-I: 1 – 2×10 -7 in any approach, TTA = 10 s - LPV-200: 1 – 2×10 -7 in any approach, TTA = 6 s Valid for unscheduled interruptions GPS_EGNOS. KPI-4 Continuity Continuity of service of a system is the capability of the system to perform its function without unscheduled interruptions during the intended operation. this metric is computed as one minus the continuity risk - APV-I: 1 – 8×10 -6 per 15 s - LPV-200: 1 – 8×10 -6 per 15 s ICAO SARPs and ICAO Doc-9849, see Additional Resources Table 6 GPS/EGNOS key performance indicators (ICAO, see Additional Resources) Procedure Approach xPE at 95% Target (m) APV-I HPE 95% 16 VPE 95% 20 LPV-200 (Cat. 1) HPE 95% 16 VPE 95% 4÷6 Table 7 GPS/EGNOS positioning accuracy targets (ICAO)

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