Blog Post
Navigation progress for indoors and UAVs
GPS World - Tony Murfin • Jul 19, 2019
CAL Analytics Presents Detect and Avoid Research at IEEE/ION PLANS
I didn’t get to this year’s IEEE/ION PLANS meeting in Savannah, Georgia, in April, but I did find a few papers that interested me. You might have read past articles of mine that looked at the challenges of indoor navigation. And, of course, unmanned vehicles technology also is one of my favorites.
So, I was pleased to find papers that addressed a few key issues for me:
- An approach that employs cooperative smartphones to achieve about 3 meters indoor location.
- Another look at the problems in using smartphone embedded GNSS for RTK positioning.
- Relative positioning between UAVs using GNSS, radio and inertial, and also adding image processing in a GNSS denied environment.
- Analysis of encounter-alerting issues for UAV detect and avoid systems.
Indoor navigation
Indoor navigation is an area which is seeing quite intense research, and several companies have now put initial products on the market. The general approach has been to use sensors within smartphones combined with radio-frequency (RF) signals which seem to be readily available in stores and malls which indoor location is finding commercial applications.
If a position can be generated by an internal GNSS receiver within the phone in an outdoor setting prior to entering a building, the trick is to carry that position forward as GNSS signals disappear when the user moves away from the entry area. Inertial sensors in the phone are usually not accurate enough to do this job on their own, so ranging using RF from Bluetooth and Wi-Fi transmitters/beacons may be integrated to provide a position solution. Magnetic sensors in the phone have also been used to detect fixed metal structures within a building and use this data to aid location determination.
The problem is that you need an up-to-date database of where the Wi-Fi and Bluetooth are located, and it has been taking a lot of work to map or “fingerprint” the interiors of buildings — and guess what, these “beacons” often are moved after a mall or store is mapped, so RF ranging can become quite inaccurate.
So, fearless investigators from the University of Buckingham and University of Northampton in the U.K. have come up with the concept of using ranging between cooperative smartphones to aid each other and achieve location accuracies of 5-10 meters.
While outdoors with good GNSS position, the inertial sensors in each phone are calibrated, each phone gets position using its internal GPS and a network is formed between the phones using their relative positions. Then when a phone goes inside the building, step counting is used to maintain relative positioning in the network. This can result in around 3 meters positioning for the interior phone.
Well, yes, not everyone has two other buddies waiting around so one guy can go in and find the classic comic store, but for applications such as firefighters, urgent/health care, and security/police, this approach might work well.
Another paper looked hard at the options there might be to resolve problems with GPS performance which has previously precluded running RTK on smartphones. If we could achieve centimeter positioning on a mass-market basis, many current applications which are inhibited by cost, could become possible and revolutionize even the way we live. People have already used external solutions to solve some of the problems, but leading researchers at Texas U, with Broadcom and Radiosense support, may have come up with a self-contained solution.
It is known that there are issues with the capability of the GNSS chip and oscillator components in smartphones — the observables they produce are not currently of sufficient quality to sustain RTK performance. So these researchers worked with Broadcom, who supplied them with an Android smartphone, which provided access to raw code and carrier-phase outputs and was also able to process these measurements internally.
Carrier phase measurements in smartphones suffer from five anomalies not found in survey-grade GNSS receivers — but four of these can be fixed in post-processing. The remaining phase measurement error increases with time and precludes RTK centimeter-level positioning — it could be the result of round-off error due to processing limitations. Otherwise it seems possible that carrier-phase differential GNSS positioning might be achievable.
However, the researchers also studied antenna performance and found that its gain pattern was significantly affected by strong local multipath. The impact is that deep, unpredictable fading and large phase error will compromise centimeter-accurate positioning.
So we’re not quite there yet, but with a new smartphone version showing up almost every other year, it is always possible that researchers and manufacturers will eventually evolve designs in the right direction, and ultimately solve the problem.
Unmanned aerial vehicles
Meanwhile, researchers at West Virginia University have been investigating methods to maintain relative positioning between UAVs in flight. With drone “swarms” and cooperative drone missions becoming more common, if a simple method could be derived to maintain relative separation, these applications could become more prevalent, especially in a GPS denied environment.
So, with only noisy ranging radios between UAVs, and an onboard navigation system solution on each vehicle, the researchers set about developing an algorithm which can maintain relative position. The solution is complicated by the geometry between the UAVs, how often range measurements are made, and the noise in those measurements. To constrain these variables, the study was run assuming the UAVs travel at the same altitude.
The study concluded that— provided the UAVs travel in the same direction, parallel to each other — that their algorithm could find a solution all the time. The focus of the study appears to be on determining hearing and relative bearing between the vehicles and results were varied depending on the frequency of range measurements, the amount of noise and the geometry. So a few steps forward along the path towards making drones work together in a hostile environment where GPS is jammed. (See “Cooperative Relative Localization for Moving UAVs with Single Link Range Measurements,” J. Strader, Y.Gu, J.N. Gross, M. De Petrillo, J. Hardy.)
Another study on the same problem of maintaining relative position between drones was also undertaken by West Virginia University, Systems & Technology Research and the Air Force Research Laboratory. However, their solution didn’t only use ranging between vehicles. It took advantage of inertial measurements on each drone, computer vision calculations derived from downwards looking cameras on both UAVs, and finally magnetometer measurements were also added into a Kalman filter solution.
With several additional sensor measurements, the researchers were able to predict that relative positioning could be maintained in a GPS denied environment. They also considered ranging radio, magnetometer and vision update rates, and the performance/update rate of various quality inertial sensors. The principle objective is to enable accurate target hand-off between drones as one approaches the other. Overall, they found their model could support 10-meter-level position and 0.5 degree accuracy.
Finally, for safe operation of UAVs in the U.S. National Airspace System (NAS), minimum Detect and Avoid (DAA) standards for small to medium size UAVs are being developed for operations within drone-accessible airspace. DAA has to provide the “see and avoid” for unmanned aircraft systems (UAS) that pilots of manned aircraft use to avoid other aircraft. So surveillance sensor information needs to supply the UAV and the remote Pilot in Command (PIC) operator with the situational awareness needed to remain well clear of other aircraft.
Part of what DAA should provide are alerts working to universal standards for all UAS.
The research presented by CAL Analytics and General Atomics (with technical support and guidance by RTCA committee SC-228 and NASA) outlined the evaluation alerts generated when other aircraft are anticipated to penetrate into a well-clear volume around a UAV.
Alerts can be “missed,” “late” and “early” — all of which can impair DAA performance and safety and which need to characterized and mitigated. Sensors currently under consideration for use in DAA include Automatic Dependent Surveillance Broadcast (ADS-B), active surveillance transponder and airborne radar — this study looked at ADS-B and radar and the trade-off that they provide related to desirable and undesirable alerts.This analysis will likely feed into the development of UAS DAA alerting standards and requirements.
Radar surveillance errors were found to increase the probability of Missed, Late, Short, Early and Incorrect Alerts, all of which is bad news for radar. ADS-B surveillance errors increased the probability of Short, Early, and Incorrect Alerts. However, ADS-B did not lower performance as much as radar — better news for ADS-B. All levels of surveillance errors were seen to increase the amount of alerting jitter, with radar seeing the most significant undesirable effects.
Highly reliable, proven DAA systems are likely an essential part of the safety system for UAS if they are to become a regular part of operations in the NAS. General Atomics has tested a DAA system including GA’s Due Regard Radar (DRR) aboard a U.S. Customs and Border Protection (CBP) Guardian Unmanned Aircraft System (UAS), a maritime variant of the Predator B UAV. The DAA system also includes Honeywell’s Traffic Alert and Collision Avoidance System (TCAS) and Sensor Tracker, specifically designed for DAA.
And, also in December of last year, a Schiebel Camcopter S-100 flew demonstration flights with an NLR-developed AirScout Detect and Avoid System. Two helicopters flew “intruder” profiles against the UAV during the demonstration. The Camcopter S-100 flew several scenarios and “unexpectedly” encountered an intruder aircraft. The system determined in real time the corrective action to maintain separation from the intruder aircraft.
So, progress on indoor navigation, research towards running RTK on smartphones, relative positioning between UAVs, and advances in Detect and Avoid solutions for UAVs. Something of a mixed bag, but all promise further progress around different solutions for a number of market navigation segments.
Originally published by GPS World.
Columbus, OH – CAL Analytics, in coordination with the Ohio Department of Transportation (ODOT), has launched a low-altitude air traffic management system for drones to support statewide operations. As the number of uncrewed aircraft systems (UAS), or drones, grows, a robust system for managing the low-altitude airspace where these aircraft operate is necessary to ensure safety. While the Federal Aviation Administration (FAA) provides air traffic control for traditional aircraft flying in certain airspaces, low-altitude traffic management for drones is the responsibility of individual operators. Currently, drone pilots are required to keep the aircraft within sight to avoid a collision. A UAS Traffic Management (UTM) system enhances safety by enabling sharing of flight details between UAS operators, providing a digital tool for flight planning, and allowing operators to eventually operate beyond visual line of sight (BVLOS) while continuing to minimize the risk of collision. “The introduction of this vital capability continues Ohio’s tradition of innovation in the aviation community while prioritizing safety,” said Rich Fox, director of the Ohio UAS Center at ODOT. “As we collaborate with others at the newly opened National Advanced Air Mobility Center of Excellence, we expect this to be the first of many industry-leading activities coming out of that state-of-the-art facility.” Following several state sponsored research efforts to determine the best way to develop and deploy traffic management for uncrewed aircraft in Ohio, this system, implemented by CAL Analytics, provides interoperability where any user can enroll to share and receive flight information. As drone technology continues to advance, traffic management will be a key enabler of BVLOS operations, which currently require special permission from the FAA once stringent safety requirements are met. “We couldn’t be more thrilled to continue our collaboration with ODOT by deploying this discovery and synchronization services to fully realize this first of a kind operational UTM capability throughout the state of Ohio,” said Dr. Sean Calhoun, managing director of CAL Analytics. “This realization is the result of a lot of industry development, including the essential work from The Ohio State University research team and sponsored research from the Ohio Federal Research Network (OFRN). We are looking forward to working with the various interested stakeholders throughout the state and the FAA to learn from this system and to start scaling UAS operations throughout Ohio.” ODOT and the City of Hilliard will be the first organizations to enroll in the system and begin exchanging information as they look to leverage UAS as a tool for everything from inspection and traffic monitoring to onsite situational awareness for first responders, such as police and fire department dispatches. “Hilliard is excited to leverage this and other airspace services that Ohio has established to enable our first responder drone operations” says Deputy Police Chief for Hilliard, Ron Clark. “These services will be critical for us to achieve FAA approval and operate our drones in a safe and effective manner.” In the coming years, more advanced and BVLOS drone operations will increase in Ohio, which means multiple operators may be flying in the same area to deliver medical supplies, perform emergency services, conduct infrastructure inspections, and even deliver commercial packages. For safe and successful scaling of commercial drone operations, it’s imperative that pilots have situational awareness for strategic deconfliction. While both private and public organizations can enroll in the traffic management system, this resource is particularly valuable for other state agencies and local governments across Ohio. These services are available at no cost to any operator or fleet manager that requests access and goes through the onboarding process. To learn more or request access, please contact CAL Analytics at info@calanalytics.com.
Columbus, OH – CAL Analytics has been selected by the Ohio Department of Transportation (ODOT) to provide statewide Uncrewed Aircraft System (UAS) operation services using CAL’s UAS Service Supplier (USS) platform. This agreement is the culmination of a multi-year build-up of CAL’s UTM service platform that started in 2019 with a $1.4M award from the Ohio Federal Research Network (OFRN) to develop an interoperable and resilient contingency management system for Ohio UAS Operations. Through this work, Ohio continues its leadership in the innovation, research, development and utilization of UAS technology. CAL’s USS will provide ODOT a wide array of services, including a centralized monitoring and management capability of statewide infrastructure, such as communications, navigation and airspace surveillance equipment, critical for UAS Beyond Visual Line-of-Sight operations. Additionally, CAL will provide ODOT with enhanced operational planning and situational awareness for its extensive statewide utilization of UAS for Visual Line-of-Sight operations. “Ohio and ODOT in particular, has been on the forefront of embracing UAS technology, so we are very excited to have our USS platform provide the basis for statewide utilization,” said Dr. Sean Calhoun, Managing Director of CAL Analytics. “We have put a lot of our system development focus making sure our platform provides a host of performance and safety related features. Our work with NASA and integrating our health and integrity monitoring capabilities into our deployments will ensure statewide systems can scale in a robust and safe way.” “CAL Analytics technology will help us take support of our uncrewed aircraft operations to the next level. Not only will our remote pilots use it for situational awareness and safety, but we are exploring the ability to expand this service to first responders across the state to better coordinate air support during an emergency,” said Rich Fox, UAS Director – Ohio UAS Center for ODOT. This agreement between CAL Analytics and the Ohio Department of Transportation is big win for the State of Ohio and the state of UAS ecosystem growth. Ohio is a leader in the Advanced Air Mobility business development aspect of UAS operations and the individuals involved in the OFRN are proud to have played a part in supporting new technology and innovation development,” said Maj Gen (Ret.) Mark Bartman, OFRN Program Executive for Parallax Advanced Research.
Columbus, OH – CAL Analytics has been awarded a NASA Phase II-E Small Business Innovation Research (SBIR) award to deploy their Health & Integrity System (HIMS) to the Ohio Department of Transportation’s Uncrewed Traffic Management (UTM) system. This will be the first-time an In-time System-wide Safety Assurance (ISSA) system will be deployed and integrated into a functioning UTM environment for operations in an urban environment. This initiative is researching ways in which the resiliency and robustness of UTM ecosystems can and should be improved. The primary result of those activities was the formulation of a flexible, service-based architecture for Health & Integrity (H&I) monitoring, assessment, and mitigation of complex, federated System of Systems (SoS). This aptly named Health & Integrity Management System (HIMS) adds another dimension of capability to the UTM architecture wherein it is intended to holistically monitor and respond to the ecosystem, providing continuity between independent UTM services from a system reliability perspective “Being able to evaluate our ISSA implementation in an operational environment that Ohio offers will be a critical step for validating the our various HIMS safety monitors and system interactions what will be key to ensuring a robust UTM ecosystem for safe low-altitude operations,” said Dr. Sean Calhoun, Managing Director of CAL Analytics. “Our HIMS system not only provides various real-time monitoring of key systems, such as surveillance and navigation, but we also provide capabilities assessing the impacts to operations and how to relay that information to operators.” The CAL HIMS system builds off the Resilienx, Inc. FRAIHMWORK platform to realize a scalable ISSA system tailored specifically to UTM applications. The open architecture approach to the ISSA system enables seamless integration of future system monitoring and scalability. The effort builds off Ohio and NASA’s existing AAM National Campaign partnership, which includes System-Wide Safety, and The Ohio State Universities UTM development effort sponsored by the Ohio Department of Transportation (ODOT). “Safety is the number one goal at the Ohio Department of Transportation, operational assurance is the most important component in any aviation operation. As we continue to move towards highly automated and remote operations in the airspace, the health of systems and sensors providing information becomes crucial to maintain the safety for transportation on the ground and in the air,” said Fred Judson, UAS Director – Ohio UAS Center for ODOT. “Safety is the key to innovation in aviation. Learning how and when to automate our safety monitoring, assessment, and mitigation functions enables us to design air systems that benefit all of us.” said Dr. Misty Davies, NASA’s Project Manager for System-Wide Safety Project.
