GPS World

Tag: GPS alternatives

  • Seen & Heard: Autonomous vehicles and Apple AirTags

    Seen & Heard: Autonomous vehicles and Apple AirTags

    “Seen & Heard” is a monthly feature of GPS World magazine, traveling the world to capture interesting and unusual news stories involving the GNSS/PNT industry.

    Image: iStock/Getty Images Plus/Getty Images
    Image: iStock/Getty Images Plus/Getty Images

    San Francisco Not Keen on Avs

    San Francisco officials aren’t happy with autonomous vehicles (AV) on their streets. They say the AVs are at fault for traffic violations and congestion, delays in emergency response and public transport — even trips onto public sidewalks. California officials granted the first AV deployment permits this year, allowing companies to release self-driving cars onto city streets and to provide passenger service as robotaxis. State governments have the legal power to grant permits to AV companies to conduct testing and ride-hail services, leaving city officials powerless to control self-driving car incidents that affect public safety.

    (Image: Apple)
    Image: Apple

    AirTag under Fire 

    Two women have filed a class-action lawsuit against Apple, claiming its AirTag trackers are being used for malicious and criminal purposes. Both women say they were tracked by ex-partners using Apple AirTags hidden in their belongings. They are seeking damages for negligence and privacy violations, and are hoping to prevent Apple from continuing to manufacture the product with “design flaws.”

    (Image: TU Delft/Frank Auperlé)
    Image: TU Delft/Frank Auperlé

    Navigating Urban Canyons with SuperGPS 

    Researchers at Delft University of Technology, Vrije Universiteit Amsterdam and VSL have developed an alternative positioning system that is more robust and accurate than GPS, especially in urban settings. The aim of the project — SuperGPS — was to develop an alternative positioning system that makes use of mobile telecommunications networks instead of satellites and that has better accuracy than GPS. A prototype of the infrastructure achieved an accuracy of 10 centimeters. The new technology is important for the implementation of a range of location-based applications, including automated vehicles, quantum communication and next-generation mobile communication systems.

    (Image: Allison Usavage/Cornell University)
    Image: Allison Usavage/Cornell University

    Robots Head to Vineyards

    Cornell researchers have designed PhytoPatholoBots (PPB) that will be deployed in vineyards across the country next spring in the first of a four-year project at Cornell, which is led by the University of Minnesota. The autonomous robots will collect data on the health of each grapevine, helping growers to evaluate their vineyards. The robots are part of the Specialty Crops Research Initiative, bringing innovation to the wine and grape industries.

  • Satelles shows improved PNT accuracy from LEO constellation

    Satelles had demonstrated in 2016 sub-microsecond timing using its Satellite Time & Location (STL) service with a stand-alone TCXO-based receiver. The service uses a signal from the Iridium low-Earth orbit (LEO) constellation.

    Now the company has released from new tests using configurations with a differential source and with a more accurate OCXO clock, producing timing accuracy of 160 nanoseconds.

    Gregory Gutt, president and chief technical officer of Satelles, made the presentation at the recent Institute of Navigation International Technical Meeting.

    The 66-satellite Iridium LEO constellation transmits overlapping spot beams, which provide location-specific data that changes every few seconds. The featured image on this article (above) shows spot beam pattern for 2 of 66 satellites.

    Overview of Satelles test configurations. (Chart: Satelles)
    Overview of Satelles test configurations. (Chart: Satelles)

    The testing employed three different configurations of equipment, services, and environment, as shown in the adjacent figure. Equipment employed in the tests included a Stanford Research Systems (SRS) rubidium vapor frequency reference, based on the PRS10 module, and a Satelles Evaluation Kit (EVK2) STL receiver, comprising a Maxim RF chip, Xylinx Spartan-3 FPGA , TI dual core DSP chip, and internal OCXO or external clock.

    Parameters and equipment for the three test configurations:

    Configuration #1 – Optimal. Outdoor antenna, Rubidium clock powered on for months prior to data collection, receiver configured in static mode with a known location, and high-quality antenna

    Configuration #2 – Sub-optimal. Indoor antenna, Rubidium clock powered on 6 hours prior to data collection, receiver configured in static mode with an unknown location, and low quality antenna

    Results from the first two tests are shown here:

    Test results, configurations 1 and 2. (Chart: Satelles)
    Test results, configurations 1 and 2. (Chart: Satelles)

    Configuration #3. Three independent receivers collecting data, receiver on-board OCXO, indoor antenna, receiver configured in static mode with an unknown location, low-quality antenna. Tests performed:

    • 10 days with no local reference station running
    • 10 days with local reference station, 20km away from test receivers, providing timing corrections to STL ground segment.

    Results from these tests shown here:

    Results from OCXO tests. (Table: Satelles)
    Results from OCXO tests. (Table: Satelles)

    With this individual test result:

    OCXO timing result with base station. (Chart: Satelles)
    OCXO timing result with base station. (Chart: Satelles)

    Some of the commercially available products and evaluation kits that incorporate the STL service are shown here:

    STL user equipment implementations. (Image: Satelles)
    STL user equipment implementations. (Image: Satelles)

  • NIST explores timing alternatives for smart grids

    The National Institute of Standards and Technology (NIST) has published a 33-page special publication reporting on the results of a workshop convened to recommend research and development priorities for alternatives to GPS time distribution in electrical power systems.

    “If timing is to become mission critical, redundant means of distributing timing information is essential,” according to NIST.

    NIST hosted the “Time Distribution Alternatives for the Smart Grid Workshop” at its Gaithersburg, Maryland, campus on March 21. The information gained will inform future NIST, U.S. Department of Energy, national laboratories and private sector technical programs and strategic planning.

    The workshop consisted of experts on both electrical power and wide-area time distribution. The experts came from industry, utilities, academia and government.

    The findings cover desired future characteristics, targets, challenges and barriers to adoption of time distribution alternatives; and priority R&D areas for time distribution alternatives.

    Potential alternatives to wide area distributed time synchronization include Enhanced WWVB (radio signal broadcasting), eLoran (hyperbolic radio navigation) and the IEEE Wide Area Precision Time Protocol (PTP – master slave clock synchronization).

    Results of the workshop illustrate the need for alternatives to existing GPS timing systems as well as backup systems and many of the challenges that need to be addressed to develop and implement alternatives. Some of the overarching themes that emerged include the following:

    • While a number of potential alternative exist, they will require further infrastructure, research and concerted investment to implement and demonstrate their potential to replace, supplement, back up, or fill gaps in existing GPS systems.
    • Potential alternatives may need to be combined in ensembles to fill gaps, create the needed redundancies, and supplement GPS-based timing.
    • Future alternatives to GPS will need to have the same or better levels of accuracy, resilience, security, trustworthiness, and availability to supplant existing systems; a diversity of timing distribution systems may be needed (terrestrial, communication-based, wireless, etc.).
    • Dependency on space-based systems is currently strong due to their perceived reliability; there is limited awareness of the possible adverse impacts of timing failure events in such systems (and few backups exist).
    • Developing and using existing alternatives and new technologies, and integrating these with legacy systems will require standards and use cases to enable new technology, architectures, and interoperability among systems.
    • Better understanding of attack and failure threat modes is needed to estimate and demonstrate the true consequences of timing failures in systems based entirely on GPS.