XPeng Motors‘ new XPeng P5 smart electric vehicle is equipped with automotive-grade lidar technology. The P5 has “navigation guided pilot” (NGP) capabilities, which will be on China’s city roads for the first time in a production vehicle, powered by XPeng’s full-stack in-house developed autonomous driving system XPILOT 3.5.
The XPILOT 3.5 autonomous driving system has a high-precision positioning unit (GNSS + inertial measurement unit, or IMU) along with 32 perception sensors — two lidar units, 12 ultrasonic sensors, five millimeter-wave radars and 13 high-resolution cameras. The sensors are fused into a 360° dual-perception system to provide sufficient redundancy to handle challenging and complex road conditions.
The double-prism lidar units are able to distinguish pedestrians, cyclists and scooters, static obstacles, and road work, in challenging scenarios such as night and low-light conditions, backlighting and alternating light-and-dark illumination in tunnels.
Extending the NGP function from highways to city diving, the P5 will be able to handle situations such as other autos cutting in, automatic follow and speed-limit optimization on urban roads, recognizing traffic lights as well as small objects.
The P5’s Xmart OS 3.0 in-car operation system supports all-voice interaction. It uses Qualcomm’s Snapdragon SA8155P auto-grade computing platform to ensure seamless user control and interaction. The instrument console includes a 15.6-inch screen with essential information and controls where the driver needs them. Xmart OS 3.0 also allows vehicle-to-home connection.
The P5 will be featured at Auto Shanghai 2021 on April 19.
The 18,000-container-capacity CMA CGM Kuergelen. (Photo: CMA CGM)
Of the 273 papers researchers presented this year at the Institute of Navigation’s annual ION GNSS+ conference, which took place in Miami on Sept. 16–20, the following five focused on maritime issues. Papers are available at www.ion.org/publications/browse.cfm.
Automating the Sharing of Ocean Weather Data
The Automatic Identification System (AIS) — mandatory for large ships and used by many mid-sized ones — was designed to help avoid collisions, enable shore authorities to provide vessel traffic services, and allow coastal states to monitor their waters. It also may be used to transmit other information between AIS stations onboard and ashore.
In the aftermath of the sinking of the container ship El Faro in 2015, the U.S. National Transportation Safety Board (NTSB) and U.S. Coast Guard found a contributing factor was lack of reliable weather forecasts. The NTSB then recommended to the National Oceanic and Atmospheric Administration (NOAA) that it determine whether AIS could be used to share weather data collected by ships, to supplement the Voluntary Observing Ship (VOS) program where ships voluntarily submit weather observations to NOAA. The paper describes a successful test of this concept.
Citation. Gregory Johnson, Ken Dykstra, Gaurav Dhungana and Brian Tetreault, “Sharing Ships’ Weather Data via AIS.”
EGNOS for Maritime Navigation
The European Geostationary Navigation Overlay System (EGNOS), which has been providing guidance to civil aviation since 2011, also can support maritime, railway and road applications. This paper assesses its use for maritime navigation compliant with International Maritime Organization (IMO) requirements for harbor entrances, harbor approaches and coastal waters: 99.8% of signal availability, 99.8% of service availability, 99.97% of service continuity, and 10 meters of horizontal accuracy. A kinematic test campaign was conducted in the waters of the Canary Islands using a geodetic multi-frequency, multi-constellation receiver-antenna pair installed aboard two vessels. The EGNOS Maritime Service met all IMO requirements by achieving a signal availability of 99.999%, a service availability in 99.9% of a predefined rectangular region, and 1.06 meters of horizontal accuracy at the 95th percentile. The service continuity requirement, however, was met in only 62.50% of the predefined region. Therefore, the paper concludes that the continuity risk is the most limiting factor for expanding the EGNOS Maritime Service along the coastal waters of the Canary Islands.
Citation. Deimos Ibáñez Segura, Adria Rovira Garcia, Jaume Sanz, José Miguel Juan, Guillermo González Casado, María Teresa Alonso, José A. López Salcedo, Huamin Jia, Francisco Javier Pancorbo Garcia, Carlos Garcia Daroca, Irene Martin Calle, Santos Rodrigo Abadía Heredia and Manuel López Martínez, “A Kinematic Campaign to Evaluate EGNOS 1046 Maritime Service.”
Options for Integrity
Many maritime authorities are considering how to maintain the integrity of navigation systems as their infrastructure ages, especially given that the need for integrity in the user position is expected to increase with e-navigation services and for autonomous vessels. In harbor entrances, harbor approaches and coastal waters, the International Association of Marine Aids to Navigation and Lighthouse Authorities (IALA) prescribes an absolute horizontal accuracy of ≤10 meters 95% of the time, with an integrity risk of 99.99999%. Today’s GNSS more than meets that accuracy requirement, so the driver is integrity. Options for integrity are marine radiobeacon DGPS/DGNSS, the primary augmentation system in use today; receiver autonomous integrity monitoring (RAIM); satellite-based augmentation systems (SBAS); and others (such as commercial services or inertial.). The European MarRINav project is investigating resilient PNT options to support UK Critical National Infrastructure. Part of this work is comparing EGNOS and marine radiobeacon DGPS performance to inform international discussions and receiver standardization.
Citation. Alan Grant, George Shaw and Martin Bransby, “Considering SBAS and marine radiobeacon corrections to support safe maritime operations.”
Evaluation of WAAS for Use in Canadian Waters
Mariners navigating in Canadian waters use a ground-based augmentation system (GBAS) that provides differential corrections and integrity monitoring of GPS. This GBAS has been provided since 1994 by the Canadian Coast Guard (CCG) in the form of a differential GPS (DGPS) broadcast service. The service is only provided south of latitude 60°N in collaboration with the U.S. Coast Guard. Before embarking on a recapitalization program of its 24-year-old DGPS, and given that the U.S. Coast Guard is progressively shutting down its National Differential GPS sites, the CCG is evaluating options for its own DGPS network. Options include the wide-area augmentation system (WAAS), originally developed by the U.S. Federal Aviation Administration for civil aviation. This paper describes the authors’ evaluation for the CCG to determine the expected accuracy, integrity and availability of WAAS throughout Canadian waters, concluding that the current WAAS provides acceptable accuracy and integrity for most of Canada, excluding the higher latitudes.
Citation. Gregory Johnson, Gaurav Dhungana and Jean Delisle, “An Evaluation of WAAS 2020+ to Meet Maritime Navigation Requirements in Canadian Waters.”
GNSS + INS for Attitude Determination
Attitude determination (AD) is an important navigation component for ships and spacecraft. GNSS enables resolving their orientation in a precise and absolute manner, by employing multiple antennas rigidly mounted on the vessel. This requires carrier-phase observations, with the consequent added complexity of resolving integer ambiguities. Inertial aiding has been extensively exploited for AD, because it enables tracking fast rotation variations and bridging short periods of GNSS outage. In this paper, the fusion of inertial and GNSS information is exploited within the recursive Bayesian estimation framework, applying an Error State Kalman Filter, which, unlike common Kalman filters, tracks the error or variations in the state estimate, posing meaningful advantages for AD. The results show that the inertial aiding, along with a constrained attitude model for the float estimation, significantly improve the performance of attitude determination compared to classical unaided baseline tracking.
Citation. Daniel Medina, Vincenzo Centrone, Ralf Ziebold, and Jesús García, “Attitude Determination via GNSS Carrier Phase and Inertial Aiding.”
A: The availability and quality of GPS in the application is critical. Industrial-grade MEMS IMUs can provide survey-grade performance when high-quality GPS is continuously available, but even tactical-grade MEMS cannot provide more than a couple of minutes of GPS-denied navigation. The level of integration between the two technologies is also important. Even comparing two systems using the same sensors, the performance is highly dependent on the ability of the system designer to leverage their respective strengths.
A: Successful integration of inertial sensors with GNSS requires understanding both the goals and environment of the application. Consider the required accuracy of attitude and position, severity of GNSS obstructions, expected dynamics and environmental conditions. Tradeoffs in size, power and cost narrow the choices, but achieving the desired performance is more nuanced. Data sheets for IMUs can also be notoriously difficult to compare. My advice is to focus on the goals and listen to the experts.
A: There is a clear need for reliable consumer-grade GNSS/INS in GNSS-degraded environments. In this case, two key aspects are: removal of measurement outliers, mostly caused by multipath; and adequate modeling of inertial errors. The first aspect is efficiently addressed via residual monitoring, especially with GNSS carrier phase. A 15-state INS error model is generally sufficient. Yet, modeling parameters and contribution of other terms such as axis misalignment must be evaluated using test data.
SPAN Land Vehicle optimizes integrated GNSS + INS performance for land vehicles during periods of extended GNSS outage, in low dynamic operating environments, or in dense urban canyons. SPAN Land Vehicle ensures that accurate position, velocity and attitude is maintained during such difficult operating environments.
NovAtel uses intelligent vehicle dynamics modelling and its patented Antenna Phase Windup technology to achieve the exceptional performance of SPAN Land Vehicle. The intelligent vehicle modeling identifies inertial measurement unit (IMU) errors in the integrated GNSS + INS system that accumulate after extended GNSS outages, and reduces the impact of those errors within the SPAN solution. NovAtel’s Antenna Phase Windup technology is used to sense changes in direction, and when combined with intelligent vehicle modelling, corrects for IMU errors in attitude (roll, pitch, yaw).
SPAN Land Vehicle performance can be enhanced even further by adding an external sensor such as a Distance Measurement Instrument (DMI), dual antennas or any other external position, velocity or attitude input. It is available on NovAtel’s entire line of SPAN supported IMUs.
