AvMap, the Italian manufacturer of GPS since 1994, presents the Ultra EFIS, a stand-alone unit providing air data, attitude, heading and altitude reference for flights.
The AvMap Ultra EFIS is a stand-alone device with a 3.5-inch ultra bright, sunlight readable LCD display. The unit is compact (1.95 inches / 49.5 millimeters installing depth) and ultra-light (5.1 oz / 145 g) compared to other products on the market (around 1 lb 9 oz / 700 g.).
Fitting in a standard 84 millimeters (3.3-inch) panel hole, the AvMap Ultra EFIS can be installed in a panel and be connected to the GPS receiver (included) and to the aircraft Pitot-static system to provide reliable and advanced ADAHRS.
Designed for light-sport, ultra light and experimental aircrafts, the AvMap Ultra EFIS contains solid-state gyros, accelerometers, magnetic field sensors, air data sensors and UAV Navigation motion processor, the outcome of more than eight years of motion and flight control experience at UAV Navigation.
“AvMap products range is extending beyond navigation to include more and more avionic tools with the objective to provide a complete AvMap Glass Cockpit system. To this purpose we are selecting the best partners in the market to work with, such as UAV Navigation,” said Simone Lazzarini, CEO at AvMap.
AvMap Ultra EFIS is the second product developed in collaboration with UAV Navigation, after the A2 ADAHRS module launched this April.
AvMap can stand alone or be integrated with EKP V. According to cockpit space availability and navigation needs, users can choose two displays or one device. The Ultra EFIS is the stand-alone solution for panel mounting; otherwise, for those who already own an EKP V, users may consider buying the A2 ADAHRS module to be used together with the cockpit docking station to complete the AvMap EFIS set. The A2 ADAHRS module extends the functionalities of the EKP V Aeronautical Navigator bringing attitude and airspeed to the moving map and converting it into a centralized Glass Cockpit System for both navigation and primary flight display.
GPS Source has received an indefinite-delivery/indefinite-quantity, firm-fixed-price contract with a maximum value of $16,613,430 for the procurement of defense advanced global positioning system receiver distributed devices (D3). The Army Contracting Command, Aberdeen Proving Ground, Md., was the contracting activity (W15P7T-13-D-C116).
GLI-FLO was developed by the defense contract engineering firm, GPS Source. GLI-FLO is a DAGR Distributed Device (D3) that can replace the position, navigation and timing (PNT) role currently required of the DAGR or other GB-GRAM devices inside a fixed vehicle platform. Designed as a single, secure access point to multiple devices requiring PNT data on a fixed vehicle platform, it saves space, weight and power (SWaP).
“The GLI-FLO contract award is an important milestone in GPS Source’s initiative for the defense market,” said Robert Horton, CEO of GPS Source. “Getting this award was a complicated process, but it helps fulfill our vision of continual innovation in GNSS Signal Availability, especially for the warfighter. We look forward to continuing to provide manufacturing and engineering support services to the Department of Defense.”
SkyTraq Technology, Inc., a fabless GNSS positioning technology company, has introduced its fast consumer-grade 50-Hz update rate S1216F8 GPS receiver module. The module supports GPS, QZSS, WAAS, EGNOS, MSAS, and GAGAN satellite signal reception. The S1216F8 receiver is based on SkyTraq’s newest 55-nm Venus 8 GPS/GNSS chipset.
The Venus 8 is a low-cost commercial GPS/GNSS chipset incorporating an IEEE-754 compliant FPU. With RISC/FPU running at 100 MHz, the S1216F8 GPS receiver module has industry leading 50-Hz update rate, very fast and accurate position/speed response, suitable for UAV, RC plane flight logging, and high-performance race car or speed boat data logging applications. When running at lower 1 Hz, 5 Hz, or 10 Hz update rate, the S1216F8 receiver can be used as a typical GPS receiver module currently available on the market.
The S1216F8 GPS receiver module measures 12mm x 16mm and consumes 26mA @ 3.3V during continuous navigation at 50-Hz update rate.
The S1216F8 is among SkyTraq’s S1216 family of form factor compatible, high-performance, low-cost GNSS modules. The S1216F8-GL GLONASS/GPS module and S1216F8-BD Beidou/GPS module both have a 20-Hz update rate.
The S1216 family of 50-Hz GPS, 20-Hz GLONASS/GPS, and 20-Hz Beidou/GPS receiver modules are in production. Datasheet, engineering sample, evaluation kit and reference design are available.
Swiss-based u-blox has been chosen by Leica Camera as provider of GPS technology for its premium M-System camera and accessory series.
Leica, which makes high-end and professional cameras, has integrated u-blox’ NEO GPS module into its new Multifunctional Handgrip M. The geotagging feature injects location data directly into each photo’s Exif header (Exchangeable image file format), allowing photos to be filed and retrieved according to where they were taken. The accessory is compatible with the new flagship Leica-M rangefinder digital camera series.
The Multifunction Handgrip M connects directly to a computer via an integrated USB socket, allowing full remote control of the camera and image access using the Leica Image Shuttle software package. The handgrip also facilitates the safe and steady handling of the camera, particularly when shooting with heavier telephoto lenses.
The handgrip’s features include a supplementary flash connector, a socket for an external power supply, and a sync socket for studio flash systems. An optional supplementary power source is also available.
“Leica focuses on providing the highest quality photographic equipment on the market,” said Stefan Daniel, director of product management at Leica Camera.“When a customer purchases a Leica, they realize they are making an investment in a robust, high-performance camera that delivers outstanding results. To meet these expectations, we design with only the best mechanics, optics and electronics. For global positioning, we chose u-blox.”
“We are proud to have been selected for our GPS technology by such a prestigious brand as Leica,” said Jochen Steinhauer, u-blox sales manager. “When you pick up a Leica camera, you immediately see and feel the high quality of every component. It is designed for perfection, a philosophy that u-blox also follows in our design of the world’s highest-quality global positioning modules.”
Watch EarthCam’s time-lapse movie of the construction progress for one of the largest ARRA (American Recovery and Restoration Act) funded projects in our nation’s history.
More than 42,000 hours of construction can be seen in just four minutes with the release of EarthCam’s official time-lapse movie for the San Francisco-Oakland Bay Bridge. After many years of construction to retrofit and transform the Bay Bridge, project teams and contractors will be celebrating all of their hard work at the opening of the updated bridge today, September 3.
The Metropolitan Transportation Commission (MTC) relied on 12 EarthCam construction cameras to document progress for the $6.4 billion bridge. In 2008, EarthCam installed a combination of live streaming video cameras and high definition time-lapse systems, all carefully documenting progress from several unique perspectives. Strategically located on the project site, each camera captured a specific view of the progress, archiving footage from 42 preset angles. During the life of the project, views of progress, as well as important information about construction-related lane closures, were made available on the Webby award-winning public web page.
EarthCam’s construction cameras captured nearly six years of progress, a powerful testament to the hard-working and dedicated bridge teams. The EarthCam Time-Lapse Production Team pored over the staggering number of images captured over the past 59 months and spent months hand-editing the archived imagery into a professional time-lapse movie.
GeoSpatial Innovations, Inc. (GSI) has released a cloud-based line design software tool for electric utility companies, GSI Designer, which it says will support seamless data collection and integration while limiting time and costs.
GSI Designer addresses the challenges of manual line design using GPS technologies on rugged mobile hardware to maintain and extend overhead and underground electric lines. It is altering traditional steps, such as tape measurements, fighting through difficult environments and dual entry of collected data.
“Implementing GSI Designer on the cloud cuts out many of the manual steps utility companies have to take in the line design process,” Carl Livingood, president of GSI, said. “The transition from paper to digital is important for our industry to embrace in order to remain profitable and efficiently improve services for our customers.”
This Software as a Service model is trending in the utility industry and offers scalable, affordable solutions for data collection and storage. “It alleviates back-end server maintenance and IT resources,” said Michael Hamsa, chief technology officer of GSI. “This allows smaller utilities to take advantage of high-end software solutions that will save them money in the long-run.”
Registration is now open for the Institute of Navigation’s (ION) Precise Time and Time Interval Meeting (PTTI) to be held December 2-5, 2013 (Tutorials will be held December 2) at the Hyatt Regency Bellevue, Bellevue, Washington. Registration and program information will be available online only.
PTTI is an annual conference sponsored by ION with a technical program designed to disseminate and coordinate PTTI information at the user level, review present and future PTTI requirements, inform government and industry engineers, technicians, and managers of precise time and frequency technology and its problems, and provide an opportunity for an active exchange of new technology associated with PTTI.
This year’s conference will feature a technical program around important PTTI issues including:
Advanced Atomic Frequency Standards Applications
High Performance Time and Frequency Transfer via Fiber
Next Generation PTTI Applications
Network Synchronization and IEEE 1588, NTP
PTTI in Space
PTTI Time and Frequency Laboratory Activities
State of the Art GNSS Timing Receiver
Metrology and Applications
Time and Frequency Transfer Applications –
Milliseconds to Picoseconds
Time Scales and Algorithms
In addition to a commercial exhibit, this year’s program includes a Panel Discussion on Near-term GNSS deployments and the impact on PTTI Applications and Performance Current and future status of: GPS, GLONASS, Galileo, BeiDou/Compass, QZSS, WAAS, EGNOS and INRISS.
This year’s conference will also feature pre-conference tutorials December 2, including
Introduction to Precise Time and Frequency
Time and Frequency Transfer
Two-Way Satellite Time Transfer (TWSTT)
Global Navigation Satellite Systems (GNSS) I & II
IEEE 1588: The Precision Time Protocol – An Overview
EU Member States have begun their independent testing of the most accurate and secure signal broadcast by the four Galileo navigation satellites in orbit.
Transmitted on two frequency bands with enhanced protection, the Public Regulated Service (PRS) offers a highly accurate positioning and timing service, with access strictly restricted to authorized users.
“Galileo is in its In-Orbit Validation phase, planned to include experimental demonstrations of PRS capabilities in terms of positioning and access control,” explained Miguel Manteiga Bautista, heading ESA’s Galileo Security Office.
PRS access was initially considered for Galileo’s Full Operational Capability phase, but it has been enabled in 2013 in response to the strong interest of Member States in this service. To allow early access to PRS during the current phase, the European Commission and ESA began the joint project ‘PRS Participants To IOV’ (PPTI) in July 2012.
ESA ensured the availability of several tools developed under ESA contracts, including test receivers and other qualification equipment. ESA also provided the critical knowhow and expertise required to conduct these experimental campaigns.
ESA’s PRS Laboratory, based at the Agency’s ESTEC technical centre in Noordwijk, the Netherlands, was used to provide training, demonstrations and sample data.
“As a result, Belgium, France, Italy and the UK have now performed independent PRS acquisition and positioning tests. In parallel, ESA, through collaboration with Dutch and Italian authorities, is also conducting PRS fixed and mobile validation in several locations in the Netherlands and Italy,” added Miguel Manteiga.
The PRS tests have demonstrated a current autonomous positioning accuracy below 10 m when in the correct geometrical configuration. This is an impressive result considering the small number of Galileo satellites in orbit and the limited ground infrastructure so far deployed.
In the case of Italy, which has developed its own PRS receiver, the tests have already confirmed the feasibility of independent PRS receiver development and verification based on specifications provided by the Eurpoean Space Agency (ESA).
ESA’s new Telecommunications and Navigation Testbed Vehicle, a mobile test platform to support test campaigns for navigation and telecommunications services, most notably Europe’s Galileo constellation.
“But the PPTI project is still ongoing in order to test more advanced functionalities this coming autumn and to run the first aeronautical PRS tests in collaboration with the Dutch authorities. Other Member States have also expressed their willingness to join the IOV PRS experimentation campaigns soon,“ concluded Miguel Manteiga.
The project is the first step to ensure the use of the PRS service as soon as it is operational. It will be complemented by the PRS Pilot Projects, focused on PRS applications, which are currently under definition in a common effort between the EU Member States, the European Commission, ESA and the European Global Navigation Satellite System Agency.
In addition to the qualification of the PRS service, these initiatives will allow the timely availability of competitive PRS receivers in Europe and the setting up of organizations in the Member States required to handle PRS, ESA said.
In the field, capture up to 200 MHz of multi-channel bandwidth and return to your lab with a rich library of GPS and GLONASS signals and impairments to accelerate RF product designs and research. Add a camera for a complete view and map of your recording environment.
Averna’s RF Studio software and suite of award-winning RF test instruments set the standard for portability, flexibility and repeatability, empowering you to efficiently record and play back all common radio, video, and GNSS signals in the highest fidelity to accelerate RF projects and reduce travel and testing costs.
RF Studio: A Powerful Software for Easy RF Recording
Available with Averna’s RF recorders and for National Instruments’ USRP, the versatile RF Studio features signal templates for quick setup and recording. With the Noise Figure feature you can view and record weak signals under the noise floor, and with the Spectrum, Power, and Histogram views you can visualize and analyze all your captured RF spectrum.
With the optional DriveView™ module, you can capture a complete visual record and map of where you made your recordings to aid analysis and troubleshooting. As well, RF Studio’s plug-in architecture supports additional hardware, channels, user inputs, remote triggering and a distributed control interface to ensure the widest possible application.
RF Studio is available with the following platforms
National Instruments’ USRP
RF Studio for the USRP is the only product on the market in its price range that offers the flexibility to cover a wide variety of use cases, thus making it a very competitive solution for general-purpose RF R&P. RF Studio gives NI USRP customers a turnkey RF R&P solution while also leveraging the flexibility and customization possibilities that have made this software-defined radio such a successful platform.
Averna’s RF Record & Playback Solutions
Our suite of RF test instruments sets the standard for portability, flexibility and repeatability, empowering RF device manufacturers to efficiently generate, record and play back all common radio, video, and navigation signals, ensuring complete test coverage and the highest quality for their RF products.
Multi-Channel, 50 MHz and 20 MHz Compact RF Recorders
From left: James J. Miller and John LaBrecque, NASA Headquarters; A.J. Oria, Overlook Systems Technologies
By James J. Miller and John LaBrecque, NASA Headquarters, and A.J. Oria, Overlook Systems Technologies, Inc.
Satellite laser ranging (SLR) and the results of combining SLR with GPS in the future will translate into significant performance advancements for generations to come, once it is fully implemented as part of the GPS III architecture. Simply put, SLR techniques will improve GPS signal performance by enhancing the accuracy of GPS orbit and clock estimates, allowing for the correction of systematic errors and limitations inherent in current GPS radiometric solutions.
This will produce higher levels of positioning and timing as new information is processed and used to update orbital models and reference frames over a period of time. Eventually this will enable user accuracy in the centimeter range, orders of magnitude better than the 1-meter average user-range accuracies accessed today. Every GNSS constellation under development will provide for SLR, because not doing so would limit their systematic accuracy and diminish the potential of their PNT services.
This SLR initiative progressed over the past decade from technical engineering exchanges to senior-level reviews and policy deliberations under the aegis of the PNT EXCOM (see Sidebar), with GPS III now poised to have laser retro-reflector arrays (LRAs) placed on board all space vehicles, beginning with number 9 (GPS-III-SV9).
The National Aeronautics and Space Administration (NASA), National Geospatial-Intelligence Agency (NGA), National Oceanic and Atmospheric Administration (NOAA), and the U.S. Geological Survey (USGS), among others, strongly support the decision by Air Force Space Command to proceed with the placement of LRAs on board GPS III satellites to enable SLR. These agencies will work together to ensure that the derived science benefits all PNT EXCOM agencies and our many constituents and users around the world.
How Satellite Laser Ranging Works
SLR to any orbiting body involves firing repetitive laser pulses towards an object equipped with some form of LRA. The laser roundtrip time is then translated into distance or range measurements (Figure 1). In our case, SLR data collected from lasing to GPS and other GNSS constellations is compared with radiometric data collected at GPS/GNSS ground monitoring stations.
Figure 1. SLR operations description.
Radiometric monitoring and SLR each have their respective strengths. Radiometric monitoring stations are inexpensive and can be densely deployed, but are susceptible to systematic errors that cannot easily be identified. SLR is a high-accuracy method, independent of radiometric positioning, that can be used to identify some of these systematic errors. The two techniques in concert will provide more accuracy to the determination of satellite orbits and clocks, strengthening the societal benefits of GPS through improved performance and more precise applications over time.
Societal Benefits of Space Geodesy
Geodesy is the science of the Earth’s shape, gravity, and rotation, and their variations over time. Modern geodetic measurements rely upon GNSS technology and techniques to understand and respond to evolving geo-hazards such as earthquakes, volcanic eruptions, debris flows, landslides, land subsidence, sea-level change, tsunamis, floods, storm surges, hurricanes, and extreme weather. In recent years, GPS radio occultation data from satellites is used by weather services to improve the accuracy of forecasts. Other benefits include the use of regional differential networks to monitor crustal movements in near real time, and guide farm machinery and construction equipment with centimeter-level accuracies.
An essential element is the ability to relate geodetic measurements to one another in space and time through a stable and accurate reference frame. Most global terrestrial reference systems set their origin to the Earth’s center of mass or geocenter. Precise knowledge of the reference frame geocenter and its relative change are needed to study regional and global sea-level fluctuations and ocean-climate cycles like El Niño, the North Atlantic Oscillation, and the Pacific Decadal Oscillation.
Reference Frames
GPS satellite ephemerides are derived from ranging based on pseudorandom noise signals and carrier-phase variations, referenced to onboard atomic clocks and a ground network of GPS monitor stations expressed in the World Geodetic System 1984 (WGS 84) reference frame. The WGS 84 reference frame is determined using the analysis of GPS satellites, and must be periodically updated by the National Geospatial-Intelligence Agency (NGA) due to geophysical processes such as tectonic-plate motion. NGA works to maintain the tightest alignment between the WGS 84 and the International Terrestrial Reference Frame (ITRF) using GPS reference sites common to both.
The more ambitious ITRF is obtained using a global network of instrumentation — GPS, SLR, Very Long Baseline Interferometry (VLBI), and Doppler Orbitography and Radio-positioning Integrated by Satellite (DORIS) — and geodetic satellites such as LAGEOS and LARES. These data are gathered and analyzed through an international cooperative effort by the services of the International Association of Geodesy (IAG) within the framework of the Global Geodetic Observing System (GGOS) (Figure 2).
Figure 2. Structure and products of the Global Geodetic Observing System related to GPS performance.
The integration of SLR and radiometric tracking of all GNSS constellations will improve multi-GNSS performance and interoperability as tools and techniques are co-located and data combined into various products that enable PNT service providers to improve system models.
Geodetic Requirements. GPS is a critical component in the determination of the ITRF geodetic reference frame and serves as the principal means of positioning relative to the reference frame. Though the current accuracy of the ITRF and WGS 84 reference frames marginally meets most current operational requirements, emerging scientific requirements in Earth observation demand more accuracy than core geodetic systems, including GPS and the ITRF, can deliver.
There is thus a growing GPS capability gap that can only be met with systematic improvements such as SLR will enable. In this manner, today’s scientific needs for positioning and timing often become tomorrow’s operational capabilities. If GPS is to continue as the primary geodetic reference system, we must ensure that GPS continues to evolve its system accuracy as well (Figure 3).
Figure 3. Evolution of GPS accuracy versus civil and scientific requirements assuming a factor of ten per decade improvement in accuracy.
Presently, the accuracy of both the ITRF and the WGS 84 is estimated to be on the order of 1 part per billion (6.4 millimeters at the Earth’s surface), with observed regional drifts on the order of 1.8 mm/year, and errors in the colocation of geodetic stations exceeding 5 mm/year. There is also little to verify this estimated accuracy of the reference frames, because successive estimates of the ITRF are retrospective and utilize the same historical data sets, except for the addition of more recent data and new analysis approaches. All determinations of the ITRF are therefore inter-related and not independent, allowing some errors to remain embedded.
Although such drifts and errors are acceptable for meter-level positioning, we must address these significant instabilities if we are to meet the growing geodetic requirements demanded by science and society. The GGOS and the National Research Council have called for a significant improvement in the accuracy and stability of the ITRF, including the goal for 1 mm of accuracy and 0.1 mm/year of stability.
Getting Laser Reflector Arrays aboard GPS III
In 2006, a working group of representatives from multiple U.S. civil and military government agencies identified a set of anticipated geodetic requirements for GPS to meet future geodesy and science needs. An analysis of alternatives (AoA) concluded that the only practical solution to correct for systematic errors in satellite coordinates and reference frames is optical laser ranging, as has been demonstrated on board GPS block IIA SV-35 and -36. These were equipped with LRAs thanks to the effort of Ron Beard of the U.S. Naval Research Laboratory (NRL).
In 2007, the geodetic requirements and AoA were submitted to the GPS Interagency Forum for Operational Requirements (IFOR), along with formal endorsement letters from NASA, NGA, NOAA, and USGS. The goal of the GPS IFOR is to ensure that new features on GPS adhere to U.S. PNT Policy objectives, and that any proposed technical enhancements do not degrade core GPS performance, schedule, signals, or services. Between 2007 and 2012, interagency IFOR discussions and studies continued and subsequently were elevated to a special multi-agency study group led by AFSPC and NASA. In December 2012, after reviewing the results of these technical deliberations, NASA Administrator C. Bolden, AFSPC Commander Gen Shelton, and U.S. Strategic Command’s Gen Kehler agreed on a plan for installation of LRAs on all GPS III vehicles beginning with SV9.
Laser-Ranging Operations
GPS laser ranging will be accomplished through the International Laser Ranging Service (ILRS), and NASA will ensure all operations adhere to a set of standards and procedures. All ILRS GPS laser ranging will use 532- or 1064-nanometer wavelengths, and the reflectivity of LRAs will be optimized for these two “colors.” To support operations and accommodate this level of control and situational awareness, the ILRS has defined minimum standards for GNSS LRA cross-sections to optimize ranging to the satellites by ILRS stations.
The design of the LRA for GPS III, funded by NASA and currently being developed by the NRL, easily exceeds the ILRS recommended standards. Some satellites tracked by the ILRS are to be ranged subject to certain basic restrictions and conditions to ensure the science data gained is optimal for all stakeholders. The ILRS has developed policies and procedures for controlled tracking, and laser ranging to GPS III will be performed on a schedule issued by the ILRS Central Bureau located at the NASA Goddard Space Flight Center in Greenbelt, Maryland.
The laser-ranging schedule will be coordinated considering ground-network capabilities, GPS operational requirements, and the tracking frequency required for accurate orbit determination. Only certified/approved ILRS stations will be authorized to perform laser ranging following a predetermined assessment, using approved laser-ranging stations operating within set technical parameters (color, power, and so on). The ILRS will issue digital keys once confirmation is received that all conditions have been met, with AFSPC and NASA maintaining a role.
Summary
A positive way forward has been established to allow for the implementation of laser ranging to the GPS-III constellation beginning with SV-9 in the 2019 timeframe. The laser ranging to GPS III, followed by post-processed analysis and mitigation of systemic errors, will contribute significantly to achieving the goal of a more accurate ITRF. These applications will also be augmented by an ongoing and significant international investment in the global geodetic infrastructure of the GGOS observing networks and analysis systems. Laser ranging of GPS III will also encourage further international investments and industry innovations as higher precisions are further introduced to the world community.
Sidebar
The PNT EXCOM
The U.S. National Space Based, Positioning, Navigation, and Timing (PNT) Policy, formally unveiled in December 2004 and supported through two administrations, strengthened GPS by creating a deputy-secretary-level PNT Executive Committee (EXCOM) to coordinate federal agency oversight of this critical national asset. The PNT EXCOM is co-chaired by the Department of Defense (DoD) and Department of Transportation (DOT), with representation by the deputy secretaries, or their equivalents, from other agencies and departments. The PNT Policy maintains the U.S. Air Force (USAF) as the DoD Executive Agent for Space.
This policy also designated newer responsibilities for other agencies. The NASA administrator, in coordination with the Department of Commerce and DOT, is responsible for developing requirements for the use of GPS and its augmentations in support of civil space systems. This level of collaboration is enabled by high-level interagency stakeholder discussions on all aspects of civil GPS activities. This is vital in the age of GPS modernization among other emerging constellations, as it allows individual PNT EXCOM agencies to develop and fund new capabilities. This multi-agency collaboration is very appropriate for GPS, since PNT is a suite of services used by all federal agencies to serve the public, providing greater safety, efficiency, and economy for a multitude of governmental missions.
Collaboration through the PNT policy has allowed NASA to optimize the use of GPS-based PNT services to fulfill a variety of science missions with ever-expanding societal benefits, ranging from space operations, exploration, Earth observation, and weather forecasting, to all manner of environmental monitoring including ice-melt and sea-level fluctuations. These data are increasingly important for governments to be able to plan for and respond to changes affecting human health, economy, and security. NASA therefore continues to work closely with the USAF and other PNT EXCOM agencies to improve the performance of GPS and its products through science initiatives.
One such initiative is known as GPS Satellite Laser Ranging (SLR), and is described here, along with its implementation aboard GPS III satellites.
Acknowledgments
The authors thank these individuals for their contributions in developing a way forward for the implementation of LRAs on GPS III, clearly showing the high level of interagency interest and coordination required to make this initiative happen overly nearly a decade of work. We are especially grateful to the U.S. Department of Defense, and in particular to U.S. Air Force Space Commander General Shelton, for leadership and support in enabling NASA and our partners to realize this important contribution to GPS in years to come: Honorable Charles Bolden, Honorable Lori Garver, Gen William Shelton, Gen Robert Kehler, Letitia Long, Maj Gen Martin Whelan, Chris Scolese, Badri Younes, Michael Freilich, Jack Kaye, Barbara Adde, Norm Weinberg, Craig Dobson, Mike Moreau, David Carter, Stephen Merkowitz, Yoaz Bar-Sever, Scott Pace, Ray Yelle, Scott Wetzel, Major Janelle Koch, Col (Ret.) David Buckman, Col (Ret.) Allan Ballenger, Col (Ret.) David Madden, Col (Ret.) Bernard Gruber, Col James Puhek, Steve Malys, Thomas Johnson, Ron Beard, Linda Thomas, Mark Davis, Larry Hothem, Ken Hudnut, Hank Skalski, James Slater, Vaughn Standley, Mike Pearlman, Erricos Pavlis, Kirk Lewis, Maj Gen (Ret.) Robert Rosenberg, and the National Space-Based PNT Advisory Board co-chaired by Honorable James Schlesinger and Col (Ret.) Bradford Parkinson.
James J. Miller is deputy director of the Policy & Strategic Communications Division with the Space Communications and Navigation (SCaN) Program at NASA. He is a commercial pilot with master’s degrees in public administration from Southern Illinois University and international policy and practice from George Washington University.
John LaBrecque is lead of the Earth Surface and Interior Focus Area within NASA’s Science Mission Directorate, managing NASA’s Global Geodetic Network that provides PNT products in support of NASA’s Earth Observation program. He received his doctorate in marine geophysics from Columbia University.
A.J. Oria works for Overlook Systems Technologies, Inc., supporting NASA headquarters in the area of GPS and PNT technology. He has a Ph.D. in astronautics and space engineering from Cranfield University, UK.
Besides my family and friends, two major influences have guided my life. One is GPS, and the other is flying, although I’m not a pilot. Most of the flying was on business trips for GPS. I’ve been writing a book about my experiences and how I helped in a small way to bring GPS to the world. I estimate I’ve spent about eight months aboard airplanes, logging almost 2.5 million miles. During that time, I visited many places throughout the world, acting as a catalyst to promote the use of GPS and to obtain GPS business for my employers and for myself. I kept an extensive log of my travels and it enabled me to recreate much of what happened, and my impressions of why events occurred.
In 1968, after two engineering degrees and five years working in communications systems, I met a business development director from Magnavox, which had teamed with Hughes Aircraft, where I worked, on a study contract. We both attended a briefing on the contract status; that day was my first encounter with what would become known as GPS.
I attended one more meeting about the 621B satellite program. The U.S. Air Force had no funding for a full-up 621B, so instead it focused on proving that the technology was viable. We were asked to bid on supplying a receiver that would precisely measure a half-mile of cable using a spread-spectrum signal. I vividly recall a Hughes VP stating that 621B would never go anywhere, and besides, Hughes was only interested in building synchronous satellites. Our 621B competitor, TRW, agreed take the follow-on contract. TRW was acquired by Northrop Grumman in 2002. The Air Force felt it needed two competitors in case one failed, so it offered a second contract to Magnavox. The company took the contract, which became its first hardware entry in the world of GPS.
Before long, I received an offer from Magnavox to join the world’s leading experts on implementing anti-jam communications systems using then-classified, direct-sequence spread-spectrum technology. Magnavox had been working in the field since it was formed in the early 1960s, building the first anti-jam modems for the Initial Defense Communications Satellite Program (IDCSP) and now pursuing a follow-on program. Its main business areas were satcom, tactical communications, and positioning programs such as the 621B receiver. There also was a group building Transit satellite receivers for the Navy. Transit was really the first navigation satellite, growing out of experiments at Johns Hopkins University Applied Physics Lab, using Sputnik signals to determine one’s position on Earth by tracking the Doppler signal of a satellite in a known orbit. Besides the Naval Research Lab, Magnavox built the only Timation receivers, an early competitor to GPS for solving military positioning needs using a satellite system.
While I was still working at Magnavox on satcom, the 621B receiver was completed and we proved you could use a spread-spectrum signal to accurately measure distance. Once again, the Air Force did not have funds to launch navigation satellites so it proceeded with a new effort called “621B User Equipment Definition and Experiments Program.” The prime contractor was Grumman Aircraft. The idea was to put four transmitters on the ground and have an aircraft with a receiver fly over them and try to determine the aircraft’s position. The signals were to look as if they came from four satellites and were received by an antenna on the bottom of the plane. Grumman decided to use a receiver built by Hazeltine, which had some experience in spread spectrum but nowhere near as much as Magnavox. For this reason, the Air Force leased another receiver from us, asking how much? We came up with the number $450,000, our development and build cost. They agreed, and we called the receiver the MX450. It flew beside the Hazeltine receiver on the NC-135 aircraft at the White Sands Missile Range. Most of the usable test data came from the MX450, showing residual errors between the aircraft solution and the range tracking system to be less than five feet. This data was crucial in getting DoD approval in 1973 to proceed with Phase 1 of GPS. But we should have called it the MX495 because we overran the cost by $45,000.
A Tale of Two Contracts
The procurement for Phase 1 GPS came together as two major contracts. There would be a small number of satellites that Rockwell would win competitively and would lead to many years and billions of dollars in future GPS satellites, as it became part of Boeing Corp. ITT would build its own payload and go on to be the major supplier of GPS payloads to this day. The other contract, a study contract, was awarded to three companies: General Dynamics Electronics (GDE), Philco-Ford, and Grumman. Two of the contractors performing that study, which ended in proposals for the design of the ground network and several types of user equipment (GPS receivers), would be chosen to create the designs. Then one of the two would be selected to actually implement Phase 1 of GPS.
After the first round down-select, we were now playing in the big leagues, GDE/Magnavox against Philco/TRW. The Philco leader, Jim Spilker, and our guru, Charlie Cahn, had to work together along with Rockwell engineers to define a common signal for GPS. The product of their work is still in use as it was defined then, at least for the civil C/A GPS signal. There were tradeoffs and compromises. The length of the short code was a contentious issue. TRW had built a 512-bit correlator, and Philco pushed that for the C/A-code. Cahn wanted 2048 bits to minimize inter-satellite signal interference. They compromised on 1024 bits. Charlie wanted a serially transmitted short code/long code for the military signal to enable long-code acquisition, a technique we had used in all our modems. But Spilker pushed for the codes to be transmitted in phase quadrature, a more elegant solution that prevailed. The need for a short code arose because the receiver could not acquire the long military signal unless it knew time to microseconds accuracy. The military code was very, very long. By first acquiring the short, repetitive C/A signal, the receiver could read its data and determine time close enough to make a long-code acquisition search practical.
The GDE/Magnavox team won the Phase 1 contract, and we were developing the first military and civil GPS user equipment (UE). Our Phase 1 UE contract included quantities of a 4-channel, high dynamics set for the F-4 fighter aircraft; a 2-channel aircraft set for the bigger and slower C-141 and helicopters; a manpack; and a civil aircraft set that looked like a TACAN and used only the C/A GPS signal. The three aircraft sets were called the X-set, Y-set and Z-set, respectively. Before long, Col. Brad Parkinson, director of the Joint Program Office, decided that there should also be a competitive high-dynamics set and another manpack, and awarded a contract to Texas Instruments. The USAF avionics laboratory wanted a piece of the GPS action so it awarded a what it called a “high technology” GPS UE contract to Rockwell Collins.
For various reasons, many not of its own making, Collins eventually became the number-one supplier of military GPS UE, long after Magnavox faded from the scene. (Hughes and then Raytheon eventually acquired the Magnavox GPS crew, where some of my former colleagues still work today.) The Collins unit flew in the C-141. Our X-set flew in a pod under the F-4. The complement of equipment, GPS receiver, navigation computer, power supply, and so on, was too big to be installed into the aircraft, so it was housed in the pod.
Building the Crew
To staff the contract required hiring many new engineers. We scoured our competitors and prior employers that had people experienced in the needed hardware and software disciplines, and were able to create a crew that went on to become major contributors to GPS developments for decades. Some started their own GPS companies, like Min Kao who, with Garry Burrel of King radio, later became the MIN and GAR in GARMIN. Another GPS company started by Magnavox people is CAST Navigation, a GPS simulator manufacturer.
The Magnavox Marine Division developed commercial Transit receiver and integrated shipboard navigation systems and survey systems. Later on, it pioneered GPS-based marine navigation systems and eventually split off into another company called Navcom, formed by Jim Litton, which later became part of John Deere. Several notable GPS experts from that Magnavox cadre like Tom Stansell, Ron Hatch (still with Navcom), and Jerry Knight are actively consulting today. So with all modesty, I have to say that I too was part of that original group who can claim some degree of fatherhood for GPS user equipment and receivers.
Over the next several years, I became an ambassador for GPS, traveling the world, particularly to visit potential military GPS users in NATO and at other allies. In the late 1970s, Magnavox and Collins were awarded the Phase 2 user-equipment developments. About a year before the production contract was awarded to Collins, I had left Magnavox to join Interstate Electronics (IEC), now a major part of L-3 Communications, to lead its efforts to become a military GPS user-equipment supplier. IEC had a unique technology for tracking submarine-launched ballistic missiles using a GPS translator tracking system. We succeeded in applying it to the DOD test ranges and for Trident missile tracking and submarine navigation. In my later years there, we eventually miniaturized the GPS receiver to the point where it could be applied to guiding missiles and projectiles.
After nine years at IEC, I decided to go out on my own as a consultant and formed Global Systems and Marketing, Inc. For the next 20 years I worked on various assignments from most of the major GPS companies and several small businesses that were trying to find a position in the GPS market. I also participated as an expert witness in many legal cases involving GPS, from patent disputes to accident reconstruction to parolee tracking.
Looking back now from the beginning of my retirement, I can obviously say I’ve learned a lot. Two things stick out in my mind:
Never believe the schedule and budget anyone offers up, because new developments will likely take longer and cost more than originally estimated;
When you stop being better, you stop being good.
I know the future holds more miraculous applications of GNSS technology because of all the brilliant, innovative people working in the field that I have met, and those that I haven’t met but have read about in places like GPS World. You are all very fortunate to be part of what I call the most important dual-use system (after the Internet) ever invented.
Len Jacobson is a retired GPS consultant, having worked in the field since 1968. He is still active in the Institute of Navigation, having been Western regional vice president twice and held leadership roles in several of its conferences. He lives in Long Beach, California. Visit his site at www.lenjacobson.com.
AvMap, the Italian manufacturer of GPS since 1994, presents the Ultra EFIS, a stand-alone unit providing air data, attitude, heading and altitude reference for flights.
