GPS World

Tag: White Sands

  • Air Force jam-proof test range ready; Galileo teendom

    Locatalite transceiver installation in the White Sands Missile Range Ultra High-Accuracy Reference System, provided by the U.S. Air Force for testing equipment under conditions of GPS jamming.
    Locatalite transceiver installation in the White Sands Missile Range Ultra High-Accuracy Reference System, provided by the U.S. Air Force for testing equipment under conditions of GPS jamming.

    Provides high-accuracy PNT even when GNSS jammed

    A critical capability to predict for GNSS chips and receivers —and for devices using alternative or back-up PNT technologies — is how they will actually perform without GPS.

    Filling this need, the U.S. Air Force 746th Test Squadron has declared Initial Operational Capability (IOC) for its new truth reference, the Ultra High-Accuracy Reference System (UHARS) at the White Sands Missile Range in New Mexico. Even when GPS — or any other GNSS system — is being completely jammed, UHARS provides extremely accurate positioning, navigation and time (PNT) over the large area that the system was designed to cover.

    “Initial testing shows that UHARS delivers accurate independent PNT as good as, or better than, the Air Force’s current Central Inertial and GPS Test Facility Reference System, so it is perfectly able to support current customer requirements,” said Jim Brewer, chief scientist of the 746th Test Squadron. “However, more data are required to tune the UHARS filter and optimize its accuracy to meet even tighter PNT requirements, which is our objective. When this is achieved, UHARS will deliver truth accuracy for next-generation military capabilities, and we will declare UHARS Full Operational Capability.”

    “UHARS is a rack-mounted, tightly integrated system of improved navigation sensors, a data acquisition system and a new post-mission Kalman filter, all of which need to work together,” said John Cao, technical director of the 746th. “It’s working very well, but once we completely measure and characterize the individual components and then tune and validate the filter, the complete system will provide a significantly more accurate reference solution for future airborne and land-based test vehicles in navigation warfare environments where modernized and legacy GPS signals are jammed from friendly or hostile systems.”

    LocataLite Transceivers. To achieve these accurate reference solutions, UHARS requires a core Non-GPS Based Positioning System (NGBPS) component capable of operating and providing sub-meter position accuracy in a GPS-denied (jamming) environment.

    The NGBPS subsystem of the UHARS program employs a network of ground-based LocataLite transceivers and test vehicle receivers manufactured by the Locata Corporation. The Locata network delivers centimeter-level positioning and navigation as well as nanosecond-level synchronization, which may be useful for military applications requiring precise time transfer in GPS-denied environments.

    White Sands is a U.S. Army rocket range of almost 3,200 square miles in parts of five counties in southern New Mexico. It is the largest military installation in the U.S.

    The LocataNet truth reference system can also provide a 2D solution to support ground-vehicle testing. Reportedly, the 2D solution, while also very good, has not yet been fully characterized. Once the filter has been fully tuned in this respect, White Sands could serve as a test facility for autonomous driving. It has many miles of paved highway, possibly in the hundreds of miles.

    The importance and uniqueness of White Sands as GPS test facility springs from the fact that it is illegal to jam GPS elsewhere without a special permit, making it extremely difficult to create a real-world test scenario to see how GPS and other PNT devices perform under denied or restricted circumstances. This is of critical importance for flight testing (UAVs and other avionics) for which the UHARS was primarily designed and optimized.

    Ligado study flawed, says NovAtel

    Method shows lack of understanding of GPS uses

    NovAtel Inc. has submitted comments to the Federal Communications Commission (FCC) regarding Ligado Networks LLC’s (formerly LightSquared) License Modification Applications.

    NovAtel raises deep concerns about the testing methodology used and conclusions presented by Ligado regarding the impact of its proposed usage of L-band frequencies for a terrestrial wireless network.

    In its filing, NovAtel identified serious flaws in the testing methodology used to evaluate high-precision receivers. Although high-precision receivers were used during the testing, the high-precision position modes that are used to achieve centimeter-level positioning accuracy required by many professional and safety-critical applications were not evaluated.

    The study shows a lack of understanding of the uses of the GPS by assuming that all applications require the same positioning accuracy, NovAtel said.

    The filing also raises a number of concerns about the potential harmful interference impact on GPS receiver performance. NovAtel is particularly concerned that Ligado has moved away from what it understood to be an agreed-upon standard that interference tolerance should be limited to a received interference signal power level that causes no more than 1-dB degradation in the received C/N0 level.

    NovAtel disagrees with the conclusion in the RAA Study that there is no meaningful correlation between a 1-dB change and GPS performance. NovAtel submits any interference must not exceed 1-dB degradation in received C/N0 if robust, precise positioning is to be maintained. Ligado has not yet proven that its use of the spectrum will not be detrimental to high-precision GNSS users, which is what the 1-dB C/N0 degradation metric ensures.

    “To date, Ligado has not proven that its use of the proposed spectrum can be made compatible with high-precision GNSS,” NovAtel said in a press release. “The interference impact on the other GNSS constellations such as Galileo, GLONASS and BeiDou has not been addressed. These constellations are increasingly used in combination with GPS for many high-precision applications. Proposed, unverified mitigation methods such as narrowband antennas are presented in the Ligado filing without explanation of who will be responsible for the cost of such design modifications and retrofit programs.”

    Galileo reaches teendom

    Europe’s 13th and 14th Galileo satellites lifted off at 08:48 GMT from Europe’s Spaceport in French Guiana atop a Soyuz launcher. (Photo: ESA)
    Europe’s 13th and 14th Galileo satellites lifted off at 08:48 GMT from Europe’s Spaceport in French Guiana atop a Soyuz launcher. (Photo: ESA)

    The Galileo constellation system now has 14 satellites in orbit after a May 24 double launch. Birds 13 and 14 lifted off together at 08:48 GMT (10:48 CEST, 05:48 local time) atop a Soyuz rocket from French Guiana. The twin Galileos were deployed into orbit close to 23,522 km altitude, inclined 57.394 degrees to the equator, 3 hours and 48 minutes after liftoff. Following days saw a careful sequence of orbital fine-tuning to bring them to their final working orbit, followed by a testing phase so that they can join the working constellation later this year.

    Marconi Prize awarded to Brad Parkinson

    The Marconi Society awarded its 2016 Marconi Prize to Bradford Parkinson. The annual prize recognizes major advances in information and communication science that benefit humanity: in this case, the difficult yet ultimately successful development of GPS. See gpsworld.com/marconi for details and a brief history.

  • Locata Tests Lead to Air Force Contract for Non-GPS Positioning System

    Locata Corporation today announced the U.S. Air Force (USAF) has signed a sole-source, multi-year, multi-million dollar contract to install the U.S. military’s first revolutionary ground-based LocataNet positioning system at the White Sands Missile Range in New Mexico. The USAF will field Locata’s new technology for extremely accurate “reference truth” positioning across a vast area of White Sands when GPS is being completely jammed.

    In a recent USAF technical report, the need for a new non-GPS based positioning capability was described by the 746th Test Squadron as the key component for “the realization of the new ‘gold standard truth system’ for the increasingly demanding test and evaluation of future navigation systems for the U.S. Department of Defense.” Locata is the new technology now contracted to enable this capability for the USAF’s future truth reference, the Ultra High-Accuracy Reference System (UHARS).

    The report documented extensive testing of Locata’s new capabilities when a LocataNet covering 1,350 square miles (3,500 square kms) was first deployed at White Sands. The USAF and the 746th Test Squadron proved a LocataNet can accurately position USAF aircraft over a large area when GPS is denied. Locata delivered accurate independent positioning as good as, or better than, the USAF’s current CIGTF Reference System (CRS). The Locata non-GPS based positioning capability is core to the UHARS that will now replace the CRS in 2014.

    After the exhaustive aircraft testing, the USAF concluded that the Locata system had not only met the extremely demanding contractual tracking and positioning requirements, but actually exceeded them on many points. Some of the milestones documented and confirmed by the USAF included:

    • The USAF report documented LocataNet position accuracy of 2.5 inches (6cm) horizontally and 6 inches (15 cm) vertically – about the size of a dollar bill – for aircraft flying at a distance of 30 miles (50km) at up to 350 mph (550 km/hr) at 25,000 feet, without GPS.
    • Throughout the period of the testing, the entire White Sands network achieved nanosecond-accurate synchronization within several minutes of the LocataNet being activated, and remained synchronized even during severe weather until turned off at the end of each test.
    • The USAF tests showed that a stock standard Locata transmitter – the same unit used in commercial applications like mining – could have an amplifier attached to easily boost signals for long-range reception. By attaching a simple, inexpensive 10 watt amplifier, the USAF proved that Locata signals could be acquired and tracked by aircraft at distances of up to 60 miles (100 km). Longer distances could be enabled by attaching higher-powered amplifiers.
    • Before to the White Sands flight trials, commercial Locata systems had only been used to position ground-based vehicles, such as cars, trucks, bulldozers and drill rigs in local areas. For the USAF tests, however, the Locata system needed to function under dynamic aircraft operating maneuvers, including banking, angular and linear accelerations, airspeeds up to 300 knots (560 km/hr), and altitudes up to 30,000 feet above sea level. The required aircraft performance was verified in the real-world testing.
    • The USAF required Locata to design, prototype and then deliver aircraft-certified antennas for use on both the Locata ground-based transmitters and the USAF aircraft. Locata worked with Cooper Antennas Ltd. of Marlow in Buckinghamshire, United Kingdom, to produce an aircraft-certified version of Locata’s new quadrifilar helix antenna design. The Cooper manufactured antennas were used throughout the tests with excellent results, and confirmed Locata’s research and analysis.

    “Locata Corp delivered a LocataNet for use in our October 2011 technical demonstration on White Sands Missile Range that provided time and position truth, independent of GPS, that was better than 18 cm (6 inches) per axis while flying at 15,000 and 20,000 foot above mean sea level profiles,” said Christopher Morin, technical director for the 746 Test Squadron. “The solutions provided by the LocataNet were within the accuracy tolerance of the squadron’s CIGTF Reference System and met our threshold objectives. Further analysis has shown that if we optimize the LocataNet deployment, characterize its errors and tightly couple its range and carrier-phase measurements with the other GPS and inertial components on the UHARS pallet into the UHARS solution post-processing software, I am confident we will be able to meet our 5-cm (2-inch) per axis truth reference objective. I am very pleased with the LocataNet’s demonstrated ability to produce an accurate, dynamic truth reference from the relatively static implementation they had already deployed in the mining industry.”

    “Locata products developed and sold by important commercial partners like Hexagon and Leica Geosystems have already shown our new technology is a game-changer for positioning over industrial-sized areas,” said Nunzio Gambale, CEO and co-founder of Locata. “However, proving Locata can provide the USAF with centimeter-accurate non-GPS positioning over a vast military area when GPS is jammed instantly elevates our technology achievements into a completely new league. It’s important to grasp the scale of what we’ve done here. The 2,500 square mile LocataNet at White Sands will be 74 times the size of Manhattan Island. It must be clear, our ability to deliver centimeter-level (inch-level) positioning over an area that large, without using GPS satellites, is both unique and totally revolutionary. No one else on Earth can do this. Many valuable industrial and consumer apps will now be built around our amazing inventions, created by Locata’s co-founder David Small and our brilliant engineers.”

    “This contract makes it clear you are witnessing the arrival of one of the most important technology developments for the future of the entire positioning industry,” Gambale declared.

    Under this new contract Locata will provide the USAF with Locata receivers and LocataLite transmitters to blanket 2,500 square miles (6,500 sq km) of the White Sands Range. Locata will also:

    a)     deliver extended hardware warranty, along with ongoing Locata software and firmware upgrades, through to the year 2025;

    b)     supply multi-year support for the installation, fielding and testing of Locata networks; and

    c)     provide long-term consultation and expert technical advice to ensure optimal operational performance of the USAF’s fielded LocataNet systems.