An Availability Prediction Method of Ground-Based Augmentation System Based on Support Vector Machine Algorithm

The Gaussian mixture model (GMM) is commonly used to model the heavy tail of the ground-based augmentation system (GBAS) range error distribution. In practice, Gaussian over-bounding based on a GMM is used to over-bound the heavy tail of the ranging errors, but the GBAS protection levels (PLs) based on the Gaussian over-bounding tend to be overestimated. Based on the idea of solution separation and overcoming the shortcoming of its direct reference to GBAS, this paper analyses the constraint conditions and objective functions of the optimal protection level based on solution separation under a GMM distribution, and proposes that multi-hypothesis solution set classification can effectively reduce the computational complexity. At the same time, least squares optimization and dynamic allocation of integrity risk are used to further reduce the protection level. This paper verifies the validity of the parameters of the GMM based on actual airport GBAS data, performs simulation verification of the typical scenarios of CAT I and CAT II/IIIa global GBAS under the Beidou 3 constellation, and analyses the performance improvement effect under different solution set traversal depths. The results show that when the traversal depths of CAT I and CAT II/IIIa are 4 and 6, the vertical protection level component of the ground ranging error is reduced by 14% and the total vertical protection level is reduced by 10%.

The positioning accuracy and integrity of the Ground-Based Augmentation System (GBAS) are impacted by the abnormal troposphere and ionosphere conditions resulting from extreme weather and intense radiation. Non-nominal troposphere error will increase the residual tropospheric uncertainty between the GBAS ground facility and aircraft. The plasma bubbles may induce signal scintillations while passing across a signal path, which could result in a loss of lock or a cycle slip. However, existing methods cannot deal with the threats caused by abnormal meteorological conditions. To reduce the impact of these conditions on GBAS, this paper describes an optimization method. By reassessing the weight matrix W in the calculation of the Vertical Protection Level (VPL), satellites that suffer from bigger pseudorange errors are assigned less importance in the positioning solution. Therefore, the positioning accuracy and integrity of GBAS are improved. Initially, we evaluate the Geometric Dilution of Precision and VPL for both single GPS and GPS+BDS constellations under abnormal meteorological conditions. The performance of different orbiting satellites in such conditions is then evaluated to further analyze their benefits in future Multi-Constellation Dual Frequency (MCDF) GBAS. The results show that the proposed optimization method can effectively reduce the influence of abnormal meteorological conditions and improve the positioning accuracy and integrity of MCDF GBAS. Moreover, mixed orbiting satellites provide more robustness against abnormal meteorological conditions and can significantly enhance the performance of MCDF GBAS.

The ground-based augmentation system (GBAS) is the cornerstone for enabling automated landings without the instrument landing system (ILS). Currently, GBAS is evolving to GBAS approach service type-D (GAST-D) for category III landings. This development toward GBAS GAST-D extends GBAS via the use of multiple frequencies (L1/L2 and L5) and the use of multiple global navigation satellite system constellations. GBAS requires correction data to be broadcast to aircraft, which is currently handled via the VHF data broadcast (VDB) datalink. However, VDB has several known shortcomings: 1) low throughput, 2) small area of operation, and 3) no cyber-security measures. In this article, we propose the use of the L-band digital aeronautical communications system (LDACS) for broadcasting GBAS correction data to address these shortcomings. In flight experiments conducted in 2019, we set up an experimental GBAS installation using LDACS. Broadcast data are secured using the timed efficient stream loss-tolerant authentication (TESLA) broadcast authentication protocol. Our results indicate that cryptographically secured GBAS data via LDACS can provide GAST-C and GAST-D services with high availability if cryptographic parameters are chosen appropriately.

According to Sheridan and Verplank's classification of levels of automation, taxiing on an airport still has a very low automation level. Key element for increased automation in taxi guidance is a precise and reliable navigation capability. As a Ground Based Augmentation System (GBAS) can fulfill the stringent requirements for a precision approach, it can play an important role in providing the required navigation performance during taxiing as well. This paper will explain the use of GBAS for taxi guidance. It presents, how the required navigation performance for automatic taxiing can be provided using GBAS. Besides the highly precision position service provided via Differential GPS, the Terminal Area Path (TAP) messages will be used to provide the aircraft with accurate and reliable information about the taxi route. Taxi trials with DLR's A320 research aircraft ATRA (Advanced Technology Research Aircraft) and the GBAS ground station at airport Braunschweig-Wolfsburg (EDVE) showed that over the whole maneuvering area the received VHF signal level was adequate for transmitting such a “Ground-TAP”. These tests were performed with an antenna on the aircraft located at a height of 8ft, which is lower than the actual required coverage minimum of 12ft defined in ICAO Annex 10. Together with a redefined voice communication structure and a list of predefined routes the use of GBAS for taxi routing functionalities of an Advanced Surface Movement Guidance & Control System (A-SMGCS) is feasible. Due to the independency from an on-board database the combination of such a message broadcast and the GNSS based positioning can be the key enabler for a future auto taxiing functionality.

Ground based augmentation system (GBAS) is the only global navigation satellite system (GNSS) with augmentation that can support category III precision approach and landing for aircrafts in the near future. The State Key Laboratory of Air Traffic Management System and Technology has developed a GBAS prototype that based on the Beidou Navigation Satellite System (BDS). Here, an assessment of BDS GBAS performance during position domain trials has been given with respect to requirements for the GBAS approach service type C (GAST C), which permits aircraft approach and landing down to the zero visibility conditions of category I approaches. The experimental results show that the accuracy of the airborne terminal is sub-meter level after the pseudorange has been corrected, and the availability of the BDS GBAS for GAST C is greater than 0.99999. The BDS GBAS is implemented within the required accuracy, integrity and availability standards for GAST C. However, due to the poor distribution of satellites geometry in some time periods, the availability of the BDS GBAS cannot meet the required criteria for GAST-D approaches. In the future, a dual-frequency and dual-constellation GBAS based on the BDS and GPS will be developed to improve the integrity and availability of the system.

Ground Based Augmentation System (GBAS) can strongly support aircraft’s precise approach and landing, and integrity monitoring is not only the difficulty of the system realization but also the key point to safeguard the flight. The ionosphere grads is the uppermost element that influence the GBAS integrity. Several algorithms are used together to achieve the ionosphere grads monitoring and ensure the ionosphere grads in an acceptable limit, ultimately guarantee GBAS integrity. In this paper, the theory basis of the ionosphere grads monitoring algorithm is analyzed firstly, then an improved algorithm is proposed, which can increase ionosphere grads monitoring sensitivity effectively. The comparable experimental analysis of present and improved algorithm is given; the results show that multi-monitoring algorithm can monitor ionosphere grads from different aspects, while the improved algorithm can increase monitoring effect apparently.

The ground-based augmentation system (GBAS) is a system for receiving supplementary information directly from a ground-based transmitter using the global navigation satellite system (GNSS). The GBAS is also used for precise approach and landing of aircraft. The antenna used for transmission and reception exhibits the quadrangular array structure of a dipole antenna having linear polarization with VHF data broadcast (VDB). However, in the case of a VDB antenna, signal cancellation and interference among individual elements may occur.In this paper, we describe an omni-directional microstrip antenna that can replace the VDB antenna used in GBAS. The proposed design reduces the ground plane in a λ/4 folded microstrip antenna in order to have omni-directional characteristics and to radiate without affecting the ground plane itself. To miniaturize the physical size of the antenna, a metal plate is added between the openings using a perturbing effect.The designed antenna is verified through simulation. The size of the radiating element is 318 mm (0.12λ) × 100 mm (0.038λ) × 221 mm (0.083λ), whereas the size of the radiating element of a λ/4 folded microstrip antenna is 568 mm (0.214λ) × 100 mm (0.038λ) × 608 mm (0.23λ). Thus, the size of the radiating element is reduced by 79.7%. As a result of the electrical characteristics of the designed antenna, S 11 is −37.1 dB, the −10-dB bandwidth is 0.56 MHz, and its gain is 1.09 dBi at a center frequency of 113 MHz. The radiation pattern shows the desired omni-directional characteristic. It is thus confirmed that the proposed antenna can replace the existing VDB antenna used in GBAS.

The integrity evaluation of satellite navigation ground based augmentation system (GBAS) is the key of the whole performance evaluation process. Aiming to solve the problems of large sample demand and low evaluation accuracy in the integrity evaluation using frequency estimation method. This paper presents a method of GBAS integrity evaluation based on the extremum distribution model. This method starts from the integrity protection mechanism, uses the positive correlation between navigation positioning error and protection level to fuse data and takes the fusion data as the evaluation sample to improve the accuracy of evaluation. Then the feasibility of using the extremum distribution model to evaluate the integrity under the condition of limited samples is analyzed based on the extremum theory and integrity risk. Further, an error controlled fusion data extremum distribution model is established and the distribution parameters are estimated by the maximum likelihood estimation criterion. Finally, the integrity risk value of GBAS in the single approach guidance is derived from the distribution model. The processing result of Beidou GBAS sample data verifies the validity of this method.

To ensure the integrity of a ground-based augmentation system (GBAS), an ionosphere-free (Ifree) filtering algorithm with dual-frequency measurements is employed to make the GBAS free of the first-order ionospheric influence. However, the Ifree algorithm outputs the errors of two frequencies. The protection level obtained via the traditional Gaussian overbound is overconservative. This conservatism may cause false alarms and diminish availability. An overbounding framework based on a Gaussian mixture model (GMM) is proposed to handle samples drawn from Ifree-based GBAS range errors. The GMM is employed to model the single-frequency errors that concern the uncertainty estimation. A Monte Carlo simulation is performed to determine the accuracy of the estimated GMM confidence level obtained by using the general estimation approach. Then, the final GMM used to overbound the Ifree error distribution is analyzed. Based on the convolution invariance property, vertical protection levels in the position domain are explicitly derived without introducing complex numerical calculations. A performance evaluation based on a real-world road test shows that the Ifree-based vertical protection levels are tightened with a small computational cost.

Ground‐based augmentation systems (GBASs) are widely used augmentation systems using satellite navigation. GBAS can improve the performance of BeiDou navigation satellite system (BDS) in civil aviation application. Evaluation is necessary before using a GBAS. On the basis of the flight trials conducted at the Dongying airport, evaluation results show that based on both the global positioning system (GPS) L1 signal and BDS B1I signal, ground accuracy designators (GADs) of four reference receivers are consistent with GAD‐C levels. The improvement in accuracy obtained with GBAS differential process is ∼60%, and the differential position error based on the BDS B1I signal is 40% greater than that of the GPS L1 signal, because currently incomplete BDS satellites distribution is worse than that of GPS. Airborne protection levels assessments show that the approach trials based on the BDS B1I signal exhibit several false alarm events. Further analysis indicates that BDS vertical protection levels were larger because of larger pseudoinverse S result from low elevation angle and unsatisfactory geometric distribution of BDS satellites. Besides, monitors show that BDS B1I signal is more affected by ionospheric delay than GPS L1 signal, which can also contribute to false alarm events.

Ionospheric fronts pose a significant threat to single frequency ground based augmentation systems (GBAS) for airplane precision approach. Here, we show our implementation of two ionospheric threat models in the DLR MASTER GNSS Simulator, a modified Spirent GSS7780/779. These threat models include the standard GBAS ”front” threat model as required for CAT-1 certification and a simplified plasma bubble model intended to represent equatorial conditions. These models can now easily be simulated at the German Aerospace Center's facilities. As an example, we simulate a GBAS ground facility (with a code carrier divergence monitor) affected by both a plasma bubble with a constant differential delay of −2 m and fronts of various gradients and speeds. Results confirm that a plasma bubble can lead to worst case position biases that may cause misleading and hazardously misleading information to be used by an approaching aircraft. Moreover, we confirm that ionospheric fronts at a speeds close to the airplane approach speed and propagating into the approach direction cause the most severe range biases. These, mapped to the position domain, can also cause hazardously misleading information.

Augmentation System (GBAS) in equatorial and low latitude regions. The ionosphere affects the propagation of GPS signals and can reduce the positioning accuracy in the equatorial and low-latitude regions. Auxiliary systems have been developed to meet the safety requirements of aviation. In this context, GBAS provide higher accuracy for differential corrections. To evaluate the performance of a GBAS, a simulation model of the GPS L1 signal-in-space has been developed, considering ionospheric delay based on statistical distributions of vertical Total Electron Content residuals obtained from IRI model and Rede Brasileira de Monitoramento Contnuo estimates, in combination with amplitude ionospheric scintillation simulated based on - probability distributions, as well as phase scintillation, generated according to empirical relationships between the indices 4 and . The GPS L1 signal model also considers clock and random errors, tropospheric delays, ambiguity, and multipath, for a complete description.

We address the differences in the ways the Instrument Landing System (ILS) and Ground-Based Augmentation System (GBAS) offer approach guidance, and their principles and methods. We perform comparative analysis of the accuracy of deviation between the GBAS Landing System (GLS) and ILS by means of flight tests, using the flight inspection aircraft at Gimpo International Airport. Our results show that the ILS deviation error increases as the distance between the threshold of runway and the aircraft increases; on the other hand, the GLS deviation error is stable, within the range of ±0.5 to ±2 m lateral and vertical deviation, respectively. We also analyze the alignment accuracy of the ILS and GLS based on the evaluation criteria of Category I of the Federal Aviation Administration, and our analysis results confirm that both systems satisfy the requirements (lateral: ±0.1°, vertical: ±0.05°).

Ground-Based Augmentation System (GBAS) is concerned with the aircraft positioning correction for precision landing. The ionospheric irregularity is a major impediment of the performance of GBAS. When an airport has at least 2 Global Navigation Satellite System (GNSS) stations, the ionospheric delay gradients can be obtained by using the dual-frequency GNSS stations. If there is only 1 GNSS station in the area, the time step-method can be used. Normally, the baseline from the time-step method is varied according to the sampling rate of GNSS data. Although the sampling rate of the GNSS receiver is a constant value, the baseline varies due to the speed of the GNSS satellite, observed from the ground reference, which can be up to 20 difference km. This paper proposes the dynamic Time-Step method which designates the baseline by adjusting the time between 2 snapshots. The results show that the range of baseline from the reference time-step method, which is set to 1 minute of the sampling rate, can be reduced to 0.5-km variation.

According to statistics from the Global Burden of Cancer Study (Globocon) of the World Health Organization (WHO), cancer, particularly breast cancer, is a severe health issue in Indonesia with 68,858 new cases and 22,000 deaths recorded in 2020. Ultrasonography (USG) technology is acknowledged as one of the potentials to support early detection, which is vital in reducing mortality from breast cancer. This study focuses on classifying ultrasound images using the Support Vector Machine (SVM) algorithm, GLCM feature extraction, Min-Max normalization, and Mutual Information with SelectKBest Feature Selection. From several experiments using the SVM algorithm with various combinations of parameter values that have been set and different Tests, namely using a Train/Test Split with a proportion of 80/20 and K-Fold Cross Validation, it shows that the SVM algorithm is capable of classifying ultrasound images of breast cancer. into two categories (Benign Tumor and Malignant Tumor) with the same maximum accuracy of 79% after applying the SMOTE Balancing Data technique or without using the Balancing Data technique. As a result, the Support Vector Machine (SVM) algorithm has the potential to be an effective model for identifying breast cancer ultrasound images, both on data from the original set that has not been balanced and data from the set that has been balanced.