NVS Technologies AG announces today, from the ION-GNSS 2012 Conference in Nashville, the launch of the NV08C-Mini PCI-E Embedded Mini PCI Express GNSS Receiver.
The NV08C-Mini PCI-E is a fully integrated GNSS receiver module, optimized for Mini PCI Express (Mini-PCIe) based applications. Its key feature is its full compatibility with GPS, GLONASS, Galileo, QZSS, COMPASS (GNSS), and EGNOS, WAAS, MSAS, and GAGAN (SBAS). It is specifically designed for use in a wide range of mobile computing, in-vehicle and rugged handheld computer equipment, for the security/public safety, telematics/fleet management, and precision GIS/survey, machine control, and agriculture markets. Features include:
Embedded mini PCI Express GNSS receiver
Very quick and simple integration
GPS, GLONASS, Galileo, QZSS, COMPASS, SBAS L1
Precise navigation, positioning, and timing
32 GNSS tracking channels / 200K correlators — Ensuring fast TTFF and high signal sensitivity
NMEA 0183 / IEC 61162-1, binary (BINR) and RTCM SC-104 v2.3 data protocols
Raw Data output — Pseudorange, Carrier phase and Doppler
Individual GLONASS group delay calibration — Assuring very high accuracy
64 KB EEPROM for firmware upgrade and data storage
Industrial operating temperature range ‐40 to +85°C
The NV08C-Mini PCI-E offers high sensitivity, high-performance acquisition and tracking, NMEA and raw data outputs, plus Differential (D-GNSS) and Assisted GNSS (A-GNSS) functions. Tracking satellites from multiple GNSS constellations ensures much higher availability of navigation signals, when compared to single constellation alternatives, and provides increased performance, accuracy, and reliability, NVS Technologies said. It features two RF channels (GPS and GLONASS), three-stage SAW filtration for high noise immunity, and several protocol interfaces and a supply voltage source for an active antenna. This fully featured embedded Mini PCI-e GNSS receiver is the quickest-to-market solution for mobile computing applications, the company said.
Altus Positioning Systems has been selected by the National Courts Administration of Norway, Land Consolidation Court Division, to provide APS-3G series GNSS survey receivers to modernize its fleet of about 80 receivers.
NavSys AS, Altus’ sales representative in Norway, won the tender in a highly competitive bid.
“The Land Consolidation Court’s rigorous tests for the selection process were completed in demanding environments, including under heavy tree canopies,” said Arnt Tore Sund, managing director of NavSys. “The price-performance relation and the quality of the Altus APS-3G receivers, together with the comprehensive customer support, detailed product knowledge and deep technical understanding of the NavSys team, strongly contributed to this successful outcome.”
The Land Consolidation Court’s 34 district offices will use the Altus APS-3G systems for geodetic, cadastre and land consolidation applications and for supporting the resolution of legal disputes.
The Altus 136-channel APS-3G is a compact, lightweight, portable GNSS RTK receiver. It is based on the high-precision Septentrio multi-frequency, multi-constellation AsteRx3 engine. The unit is completely configurable from the data collector via Bluetooth for either base or rover operation with the internal UHF radio or for network rover operation with the internal quad-band GSM/GPRS modem. Its removable 2-GB SD card enables plug-and-play of raw data transfer for post processing.
The APS-3GX model, which also is being delivered, optionally provides a port to a remote lightweight antenna that can be mounted on a five-meter pole to improve reception of the GNSS signals by raising the phase center when under dense vegetation.
Neil Vancans, president and CEO of Altus Positioning Systems, commented, “This substantial order, obtained through the efforts of our valued sales partner in Norway, is an important validation of our APS-3 technology, which offers significant competitive benefits and advantages over other higher-priced GNSS survey receivers on the market today.”
The Land Consolidation Court of Norway is a special court established under the Land Consolidation Act to adjudicate boundary disputes among property owners and freeholders in land consolidation cases. Mapping and other technical work is done by staff from the court so that decisions made are documented for the future. The technical staff has competency to do all the technical work in each case handled by the court.
By Thomas Pany, Nico Falk, Bernhard Riedl, Tobias Hartmann, Günter Stangl, and Carsten Stöber
Innovation Insights with Richard Langley
WHAT IS THE IDEAL GNSS RECEIVER? Well, that depends on what you mean by “ideal.” If we take it to mean the simplest, conceptually, yet the most capable and adaptable receiver, then we would just connect an analog-to-digital converter (ADC) to an antenna and pass the converter’s output to a digital signal processor whose software would transform the received signal into the desired result with the utmost speed and precision. There are certain technological limitations that currently preclude fully developing such a device but we are getting very close to the ideal and practical implementations already exist.
Such a GNSS receiver is an example of a software-defined radio — a radio-communications architecture in which as much of the operation of a receiver (or a transmitter) as feasible is performed by software in an embedded system or on a personal computer (PC).
Now, we can’t simply connect an ADC to an antenna since the strength of GNSS signals falls well below the sensitivity threshold of real ADCs and those that can directly digitize microwave radio frequencies are rather power hungry. Therefore, the front end of a real software GNSS receiver includes a low-noise preamplifier, filters, and one or more downconverters to produce an analog intermediate-frequency signal that passes to a high-speed ADC. The digitized signal is provided at the output of the front end in a convenient format, which, for processing signals on a PC, is typically USB 2.0 with its maximum signaling rate of 480 megabits per second. All baseband signal processing is then carried out in the programmable microprocessor.
Software GNSS receivers offer a number of advantages over their hardware cousins. Foremost is their flexibility, which permits easy and rapid changes to accommodate new radio frequency bands, signal modulation types and bandwidths, and baseband algorithms. This flexibility is beneficial not only for multi-GNSS operation but also for prototyping algorithms for conventional hardware designs. Another advantage is their use in embedded systems such as smartphones and wireless personal digital assistants. Software GNSS receivers are also a boon for teaching, where a student can tweak a particular operating parameter and immediately see the effect. And given their remarkable flexibility, software GNSS receivers can be adapted to a variety of special scientific and engineering research applications such as reflectometry and signal analysis.
In this month’s “Innovation,” we look into the development and capabilities of one modern software GNSS receiver in an effort to answer the question “What is the ideal GNSS receiver for precise positioning research?”
“Innovation” is a regular feature that discusses advances in GPS technology andits applications as well as the fundamentals of GPS positioning. The column is coordinated by Richard Langley of the Department of Geodesy and Geomatics Engineering, University of New Brunswick.
Personal-computer-based software receivers have found broad use as R&D tools for testing new signal processing algorithms, for analyzing received GNSS signals, and for integrating various sensors with GNSS. Software receivers also provide a consistent framework for GNSS signal samples, correlator values, pseudoranges, positions, assistance data, and sensor (inertial) data, and often act as integration platforms for prototype navigation systems. The distinctive feature of PC-based software receivers is their ability to work in post-processing mode in addition to real-time operation and the support of high-performance central processing units (CPUs).
So far, software receivers are typically not used as operational receivers — neither in the mass market, nor in the professional sector, nor as a reference station where a PC would already be available. The last point can be explained by the fact that most software receivers can only process a limited number of frequency bands (sometimes just L1) and are often limited to small bandwidth signals (such as that of the L1 C/A-code signal or the L2 civil signal (L2C)). Improvements of the PC-based software receiver SX-NSR achieved at the end of 2010 and in early 2011 try to overcome these limitations. They include the first real-time implementation of P-code processing on L2, a unique method for processing the ultra-wide Galileo AltBOC signals on E5, and a method to synchronize two NavPort-4 frontends (each supporting four frequency bands of 15 MHz bandwidth) via a hardware link.
The SX-NSR, which has been developed in cooperation with the Universität der Bundeswehr München in Munich, Germany, runs under the Windows operating system (XP or 7) and supports processing of GNSS signals plus sensor data (such as that from an inertial measurement unit, or IMU) in real time and in post-processing mode. It supports all the civil GPS, GLONASS, Galileo, and Compass signals. User-defined signals can be included by providing the pseudorandom noise (PRN) codes and the associated tracking parameters.
The computational real-time performance can be characterized by two rules-of-thumb for acquisition and tracking. Acquisition is based on a flexible coherent and noncoherent integration and may be accelerated by a graphics card based on the Compute Unified Device Architecture (CUDA) — a parallel-computing architecture developed by Nvidia for graphics processing but also useful for accelerating non-graphics applications. Depending on the graphics card type, a few million or many millions of equivalent correlators are available to detect even the weakest signals quickly. Stable tracking is done with multiple correlators. An x86 CPU core supports around 20 channels (for a laptop) to 30 channels (for a PC) at an average CPU load below 50–60 percent. With that CPU load, the software has enough reserve (in terms of the size of the sample buffer) to cope with latencies introduced by the non-real-time Windows operating system. In post-processing, a virtually unlimited number of channels or correlators is available.
The SX-NSR software typically connects to the NavPort-4 front end via a single USB 2.0 connector. One front end supports four RF paths with 15-MHz bandwidth in the L-band. One band is sampled at 40.96 MHz with 12-bit precision. Small batches of samples are transferred with 12 bits at regular intervals to the PC for increased spectral analysis possibilities but the continuous transfer is usually done with just 2 bits. Decimation by a factor of two (yielding a sample rate of 20.48 MHz) and/or bit reduction are options to limit the data transfer bandwidth on the USB bus. The NavPort also includes configurable notch and finite-impulse-response (FIR) filters working with 12-bit precision and 40.96-MHz data rate. The SX-NSR further supports standard output formats (such as Receiver Independent Exchange (RINEX) format or that of the Radio Technical Commission for Maritime Services (RTCM)), has a graphical user interface, and a freely user-accessible application programming interface (API) in the C programming language.
A reference station was established with the SX-NSR for the International GNSS Service (IGS) Multi-GNSS Experiment (M-GEX) starting on February 1, 2012, at the Observatory Graz in Austria (marker name GRAB). The data is routinely processed by the European Reference Frame analysis center at Observatory Lustbuehel, Graz, Austria, with Bernese Software 5.0, and shows results with a quality that is virtually no different than that of commercial hardware receivers.
All-in-view tracking of the four GNSS constellations on all frequencies (see TABLE 1) has been achieved with an off-the-shelf $1,000 PC, two synchronized NavPorts, and the SX-NSR software. In particular, the front end receives Compass B1, B2, and B3 signals and currently the software is tracking two of the geostationary Earth orbit (GEO) satellites, a few of the inclined geosynchronous orbit (IGSO) satellites, and the medium Earth orbit (MEO) satellites at Graz on B1 and B2. There are plans to implement tracking of the B3 signal for the M1 satellite and that of satellite-based augmentation system (SBAS) satellites on L5.
Table 1. Frequency bands supported by the dual NavPort-4 receiver.
Typical received carrier-to-noise-density-ratio (C/N0) values recorded at station GRAB are shown in FIGURE 1. Freely accessible GRAB data in RINEX format can be downloaded from several data archive sites (see Further Reading online).
The SX-NSR software receiver provides a GNSS development and research framework with the API opening it up for user-implemented algorithms. The user may implement only small portions of new code (such as a special acquisition technique) and for the rest of the receiver rely on the well-known behavior of the SX-NSR’s framework. A number of applications are possible using the flexibility of a software receiver; some of them are described in this article.
Figure 1. C/N0 values for five typical satellites, one each for GPS, GLONASS, Galileo, Compass, and the European Geostationary Navigation Overlay Service (EGNOS) SBAS as recorded at Observatory Graz.
The Front End
The front-end frequency plan was adjusted to have a clean spectrum free of internal interference. This is of utmost importance as software receivers are often used to detect and mitigate interference especially for the Galileo E5 and E6 frequency bands due to overlapping radio navigation services.
An inter-front-end link enables synchronization of two NavPort-4 devices. It generates a synchronous reference clock for a proper phase relationship. Moreover, a trigger is used to adjust the digital data stream of both devices. One possible application of the inter-front-end link technology is to easily double the number of available GNSS frequencies. Another possible application is the building of a dual-antenna solution. For this purpose, each NavPort-4 device handles the same GNSS frequencies, but from different antennas. Whereas within each NavPort, a quad analog-to-digital converter (ADC) synchronously samples the four received GNSS signals, the synchronicity between two NavPorts is more complex.
For the inter-front-end link, both devices have to use the same 10-MHz clock reference for a synchronous setup. This is reached by using the reference clock output of the master device as reference clock input of the slave device as depicted in FIGURE 2. It is also possible to connect both NavPort-4 devices to a single external clock reference.
Figure 2.
Each device generates its own 40.96-MHz sample rate from this reference. The phase difference of the 40.96-MHz sample rate is measured in the master and slave with a phase detector. The first input of the detector is the local 40.96-MHz clock. The second input is the 40.96-MHz clock from the other NavPort-4 with a different phase alignment due to ambiguities in its generation and cable delay. The phase detector measures the phase difference between both clocks. The low-pass-filtered output of this measurement is digitized with an ADC. If this measurement is within a phase range of ±7 degrees at 40.96 MHz, which corresponds to ±14 centimeters, the coarse synchronization is finished. If the value is not within this range, the synchronization algorithm repeats.
After starting the data processing for both devices simultaneously with an implemented digital trigger, the phase difference between master and slave clock could be measured continuously for later fine-tuning in the SX-NSR to achieve an accuracy of much below 1 degree at 40.96 MHz, which corresponds to ±2 centimeters.
The synchronization algorithm is verified by connecting two L1-capable NavPorts to the same antenna. The phase and code delay can then be determined from receiver single-differences of GPS L1 C/A-code-derived phase and code measurements. Actually, this delay estimation is part of an attitude solution (see below) and an example is shown in FIGURE 3. The code delay here is around 50 centimeters and includes the RF filter delay difference of around 40 centimeters (which can be calibrated and is stable over power cycles) in addition to the synchronization delay (here around 10 centimeters). The phase delay is naturally determined modulo one cycle and shows warm-up effects of 1.4 centimeters during the first few minutes of operation.
Figure 3. Inter-front-end hardware delay variation on a GPS L1 signal.
GNSS Reference Station
Although the GPS modernization process is ongoing and more and more L2C-capable satellites are in orbit, tracking of the encrypted P-code signal on L2 is still a key element for any receiver to be considered as a reference station or geodetic receiver. Dual-frequency observations need to be available for the full GPS constellation. A possible option to retrieve full wavelength carrier-phase observations and code ranges on L2 is cross-correlation tracking of the encrypted P-code signal. The receiver computes the cross-correlation function between the raw L1 and L2 samples over a long coherent interval as shown in FIGURE 4. The encrypted P-code stream, identical on L1 and L2, is represented by c(tµ).
Figure 4. Cross-correlation block diagram.
A receiver internal complex carrier is generated (see frequency compensation in Figure 4), whose frequency equals the Doppler shift frequency plus the intermediate-frequency difference between L1 and L2. This frequency is generally different for each satellite. The L1 signal is delayed to compute the cross-correlation function for several code-phase taps.
The cross-correlation function is computed using the predicted Doppler difference based on the Doppler frequency estimated from L1 with complex-valued baseband samples. A number of batches are collected and a post-correlation fast Fourier transform is applied. The parameter values shown in TABLE 2 result in a total coherent integration time of 6.4 seconds.
The result is the cross-correlation function as a function of code phase and Doppler. Using interpolation techniques, the position of the peak is determined, which then gives the delay and Doppler shift of the L2 signal with respect to the L1 signal. The complex argument of the peak value gives the L2-L1 carrier-phase differences. Those differences are filtered and are then added to the L1 parameters to give the L2P code estimates.
We use two first-order Kalman filters (one for the code, one for the phase) to smooth the cross-correlation estimates. The code filter is updated with the estimated delay and the Doppler; the phase filter is updated with the estimated Doppler and phase. Cycle slips are detected if the L1-L2 phase changes are too high. Loss-of-lock is detected by comparing the estimated L2 C/N0 value against a threshold. After several Kalman filter tuning steps, the L2P signal is tracked down to low elevation angles. For example, the GPS Block IIF satellite PRN1 was tracked over a whole pass without cycle slips as shown in the code-minus-carrier plot in FIGURE 5.
Figure 5. Code minus carrier-phase measurements for GPS PRN1 at site GRAB on day of year 106, 2012.
One of the key applications of a professional GNSS receiver is its use as a GNSS reference station. Using a software receiver for this purpose would also provide increased monitoring capabilities to detect (un)intentional inference via RF spectral analysis or to detect signal anomalies due to satellite failures or multipath. Furthermore, it is useful for a number of scientific experiments and research topics such as scintillation monitoring or atmospheric occultation studies.
Other GNSS Signals
The inclusion of new GNSS signals in a software receiver is typically straightforward. The PRN codes need to be loaded and the tracking parameters (such as carrier frequency, integration time, error correction scheme, phase relation of signal components data/pilot, correlator positions, and discriminator type) can be selected without source code modification. If a hand-over from a different signal is performed (such as from GPS L1 to GPS L5) and if the first signal has already been synchronized to the transmit time by decoding the time-of-week, then it is possible to directly resolve the code ambiguity of the new signal. If this is not possible, a navigation message decoder has to be implemented to retrieve the time-of-week, which mostly has to be in the source code.
Galileo AltBOC. An important exception to this rule is the Galileo AltBOC signal due to its high bandwidth. A conventional view on the AltBOC signal processing would require a sample rate of at least two times the total signal bandwidth. Depending on how many outer AltBOC side lobes are considered, this results in a sampling rate of 102 megasamples per second or more. This is undesirable for a cost-efficient software receiver solution, regarding the data transfer and the CPU load. The AltBOC processing inside the SX-NSR relies on the fact that both frequency bands E5a and E5b are sampled coherently and this coherency can be exploited to reconstruct the full AltBOC signal. The accuracy of the AltBOC navigation signal is concentrated in the main BOC sidelobes itself. More specifically, the thermal noise and multipath performance are dependent on the Gabor bandwidth, which represents the curvature of the correlation function at the tracking point. Thus a similar Gabor bandwidth can be obtained by sampling the E5a and the E5b band separately. This is the key idea of the resulting AltBOC processing scheme.
The E5a and E5b signal samples are generated synchronously inside the same ADC chip and are transferred via the USB bus to the PC running the SX-NSR. The SX-NSR first acquires and tracks the signal separately on E5a and E5b. As it is quite efficient to run the E5a and E5b tracking on separate threads (and on separate CPU cores), the combination of E5a and E5b correlation values to E5 correlation values is done at the post-correlation level.
There is no feedback from the E5 channel to the E5a/b channels. The channel maintains its own numerically controlled oscillator (NCO). A dedicated transformation is used to account for NCO differences between the E5a/b NCO values and the E5 NCO values. It is basically a sinc-interpolation in the code-phase direction and accounts for Doppler and carrier-phase differences. The transformed correlation values are added and yield an approximation to the AltBOC correlation function.
The E5 correlation values are used to compute the discriminator values to update the E5 tracking loops. The E5 NCO values are used to compute the code pseudoranges and carrier-phase measurements, the Doppler frequency, and the C/N0 values, which are the primary outputs of the E5 receiver. Although the E5 receiver is a somehow a virtual receiver (that is, without correlators), it has the same user interface including most of the configuration parameters, output (for example, multi-correlator), and API.
With AltBOC tracking, the Galileo satellites deliver code and phase measurements on five different carrier frequencies. A code-minus-carrier plot is shown in FIGURE 6. The code accuracy of the AltBOC signal is striking. The E6 signal is severely impacted by the present interference, and phase tracking is only possible for higher elevation angles.
Figure 6. Code minus carrier-phase measurements for Galileo PRN12 at site GRAB on day of year 104, 2012.
Polyfit and Vector Tracking
A software receiver should provide a transparent way to retrieve pseudorange measurements that is well understood and can be well modeled. It should also provide a flexible input to control tracking NCO values. Both points are important if the receiver is part of larger navigation system (such as an integrated GNSS/INS system). Conventional delay-lock loop (DLL) / frequency-lock loop (FLL) / phase-lock loop (PLL) configuration is one option and is well understood by all GNSS researchers and engineers. It has, however, two major drawbacks. The loops introduce time correlations that cannot be easily modeled in a positioning Kalman filter, especially if low bandwidths (carrier aiding) are used. Second, the internal parameters of a DLL are difficult to match to a deeply coupled GPS/INS system.
One way to overcome this is a method called polyfit tracking based on a rather old Jet Propulsion Laboratory patent (U.S. Patent No. 4821294). The idea behind this is to decouple pseudorange determination from the NCO counters. This is accomplished by forming the pseudoranges at the integrate-and-dump rate (such as 50 Hz) and to add the discriminator values to them. The resulting pseudorange is then obtained via a polyfit over the measurement interval.
The time correlation of the measurements is solely determined by the discriminator values, and they compensate for the NCO correlations. A nice example is the application of this method to vector tracking. In vector tracking the NCO values are determined via a line-of-sight projection of the last position, velocity, and time (PVT) estimate and this estimate is usually slightly delayed. Furthermore, the line-of-sight projection is not perfect due to inevitable modeling errors (such as atmospheric delay errors). Thus the NCO does not follow the received signal as well as for DLL/FLL/PLL tracking. This is not a problem as the difference is captured in the discriminator values. FIGURE 7 shows the output of the method for a measurement interval of 0.5 second, one GPS C/A-code signal and for a dynamic user. The PVT update happens with a delay of about 100 milliseconds, changing the Doppler frequency. This resulting phase slope discontinuity is nicely compensated by the phase discriminator. The actual measurements are marked as brown stars in Figure 7. The method can also be applied to slave a channel to a master channel. This is useful for reflectometry, for example, where the master channel locks onto a line-of-sight signal and the slave channel tracks the reflected signal from sea surface.
Figure 7. NCO-based phases (green) plus discriminator values (yellow) and polyfit for carrier-phase, code, and Doppler tracking (dynamic user, GPS C/A-code tracking).
With multiple correlators (for example, nine correlators equally spaced from -0.5 to 0.3 chip for GPS C/A-code tracking), the polyfit method can be extended in a natural way to estimate and mitigate multipath. Using the polyfit carrier estimate, the multi-correlator values are coherently combined over the measurement interval and then a correlation function model is fitted to it. An eventually presented data bit is estimated and wiped off. The correlator fit starts with the assumption that only the line-of-sight signal is present. If the chi-squared value is above a certain threshold, the correlator fit is repeated assuming additionally one multipath signal. Up to two multipath signals can be estimated.
The performance of this method can be tested with an RF signal generator. The scenario includes the line-of-sight signal (GPS C/A-code) and one multipath signal. The initial multipath delay is 0 meters and increases slowly (5.7 millimeters per second). The standard tracking method uses a multipath-mitigating double-delta code discriminator formed from four correlators (-0.2, -0.1, 0.1, 0.2) and an arctan carrier discriminator. Standard tracking is used to control the NCO values. FIGURE 8 shows that multipath is detected for delays larger than 15 meters. The detection performance depends on the carrier-phase difference of the line-of-sight and multipath signal, but for delays larger than 32 meters, multipath is always detected. If multipath is detected, the corrected ranges and C/N0 values are significantly improved.
Figure 8. SX-NSR real-time carrier-phase multipath detection and mitigation performance for a GPS C/A-code signal with a -10 dB multipath signal (standard tracking shown in black, multipath-estimating discriminator output shown in red).
The polyfit method is used routinely in the reference station and has also been tested in a dynamic scenario. A bus drive near the IFEN office in Poing, Germany, with the antenna mounted on the roof has been carried out. Even in this rural area, short-term shading and multipath severely distort single channel (DLL/PLL) tracking causing rather large position errors (red dots in FIGURE 9).
Source: Thomas Pany, Nico Falk, Bernhard Riedl, Tobias Hartmann, Günter Stangl, and Carsten Stöber
With a simple switch in the software, the NCO control can be switched from DLL/PLL to vector tracking (polyfit tracking is always on with the same fit parameters). If the standard point positioning (SPP) solution is used to control the NCO values (yellow dots), the errors are already drastically reduced because the NCOs follow the position and not the reflected signals. Also, erratic NCO jitter preceding loss-of-lock events is now eliminated. A further improvement is achieved if the PVT solution is computed by a Kalman filter (green dots), giving finally the typical high-navigation accuracy of modern GNSS receivers even with partial signal blocking.
Dual-Antenna Heading Determination
The bus drive mentioned above has actually been carried out with two antennas on the roof top with the aim of demonstrating the dual-antenna performance of the software receiver to determine heading. Two synchronized NavPorts have been used, both receiving GPS C/A-code signals (more frequencies would even be more beneficial and possible, but such a test has not yet been carried out). The software is fully prepared to handle data streams from two antennas and one option is to use the same NCO for both antennas. That is, the master antenna data is used to realize vector tracking and the discriminators of the slave channels capture the relative movement of the slave antenna to the master antenna. Again, polyfit tracking provides a natural framework to cope with this data.
Attitude is determined with receiver single-difference observations. It is beneficial to form this difference as early as possible in the receiver processing, that is, immediately after correlation. Thus carrier-phase tracking is based on receiver single-difference correlators, being the product of the complex-conjugate master prompt correlator and the slave prompt correlator (both obviously for the same GNSS signal). The heading is shown in FIGURE 10. As reference, a GPS/INS system was used that calibrated the IMU during the first 300 seconds. One sees that the polyfit plus difference correlator is able to track the carrier phase continuously over 400 seconds in the rural test drive, although there is high multipath and some shading even for the high-elevation-angle satellites. Switching off only one option (vector tracking or the difference correlator) introduces cycle slips and corrupts the heading solution.
Figure 10. Heading and heading error for the dual-antenna test.
Conclusions
Currently, we see two main applications for software receivers. First, they may replace hardware receivers if the increased software receiver performance/flexibility justifies the increased power consumption and size. Several features have been shown in this article, and the possibility to do post-processing and the high-power CPU for customized algorithms are striking arguments for software receivers. On the other hand, software receivers may be customized by inserting user-specific code via the API offering enormous possibilities.
Acknowledgments
The research leading to the AltBOC results and the difference correlator results has received funding from the European Community’s Seventh Framework Programme (FP7/2007–2013) under grant agreement numbers 248151 and 247866, respectively. This article is based, in part, on the award-winning paper “Wide-band Signal Processing Features for Reference Station use of a PC-based Software Receiver: Cross-correlation Tracking on GPS L2P, AltBOC and the Inter-frontend Link for up to Eight Frequency Bands” presented at ION GNSS 2011, the 24th International Technical Meeting of the Satellite Division of The Institute of Navigation, held in Portland, Oregon, September 19–23, 2011.
Manufacturers
The IFEN GmbH NavPort/SX-NSR receiver at station GRAB is fed by a Leica Geosystems AG LEIAR25.R4 antenna with a LEIT radome. The kinematic test used a NovAtel Inc. SPAN GNSS/inertial system.
THOMAS PANY works for IFEN GmbH in Poing, Germany, as a senior research engineer in the GNSS receiver department. He also works as a lecturer (Priv.-Doz.) at the Universität der Bundeswehr München (UniBwM) in Munich, Germany. NICO FALK works for IFEN GmbH in the receiver technology department. BERNHARD RIEDL works for IFEN GmbH as product manager for SX-NSR. TOBIASHARTMANN works for IFEN GmbH in the receiver technology department. GÜNTERSTANGL is an officer of the Austrian Federal Office for Metrology and Surveying and works half time at the Space Research Institute of the Austrian Academy of Sciences. CARSTENSTÖBER is a research associate at UniBwM.
FURTHER READING
• Authors’ Proceedings Paper
“Wide-band Signal Processing Features for Reference Station Use of a PC-based Software Receiver: Cross-correlation Tracking on GPS L2P, AltBOC and the Inter-frontend Link for up to Eight Frequency Bands” by T. Pany, N. Falk, B. Riedl, T. Hartmann, J. Winkel, and G. Stangl in Proceedings of ION GNSS 2011, the 24th International Technical Meeting of the Satellite Division of The Institute of Navigation, Portland, Oregon, September 19–23, 2011, pp. 753–766.
• Software GNSS Receiver Algorithms and Implementations
Digital Satellite Navigation and Geophysics: A Practical Guide with GNSS Signal Simulator and Receiver Laboratory by I.G. Petrovski and T. Tsujii with foreword by R.B. Langley, published by Cambridge University Press, Cambridge, U.K., 2012.
Navigation Signal Processing for GNSS Software Receivers by T. Pany, published by Artech House, Norwood, Massachusetts, 2010.
A Software-Defined GPS and Galileo Receiver: A Single-Frequency Approach by K. Borre, D.M. Akos, N. Bertelsen, P. Rinder, and S.H. Jensen, published by Birkhäuser, Boston, 2007.
Fundamentals of Global Positioning System Receivers: A Software Approach, 2nd Edition, by J. B.-Y. Tsui, published by John Wiley & Sons, Inc., Hoboken, New Jersey, 2005.
• Galileo Signal Tracking
“Performance Evaluation of Single Antenna Interference Suppression Techniques on Galileo Signals using Real-time GNSS Software Receiver” by A.S. Ayaz, R. Bauernfeind, J. Jang, I. Kraemer, D. Dötterbock, B. Ott, T. Pany, and B. Eissfeller in Proceedings of ION GNSS 2010, the 23rd International Technical Meeting of the Satellite Division of The Institute of Navigation, Portland, Oregon, September 21–24, 2010, pp. 3330–3338.
“The International GNSS Service in a Changing Landscape of Global Navigation Satellite Systems” by J.M. Dow, R.E. Neilan, and C. Rizos in Journal of Geodesy special issue, “The International GNSS Service (IGS) in a Changing Landscape of Global Navigation Satellite Systems,” Vol. 83, Nos. 3-4, 2009, pp. 191–198, doi: 10.1007/s00190-008-0300-3.
Geneq Inc. has launched the SXBlue III GNSS, a palm-sized GNSS RTK receiver that uses both GPS and GLONASS for real-time centimeter accuracy. Via Bluetooth, it brings centimeter accuracy to any smartphone, handheld, tablet, or notebook computer that is Bluetooth-compliant.
According to the announcement, the SXBlue III GNSS uses new, patented technology that allows it to generate corrections for both GPS and GLONASS satellite data even if the user’s reference station (or RTK network) only supports GPS. This opens up productivity benefits of GLONASS to all high-precision users around the world, and not just ones who have access to GLONASS-enabled reference stations, Geneq said.
“With its competitive price and creative implementation of GLONASS, the SXBlue III GNSS will open new doors for users who want to improve their productivity with GLONASS but don’t have control over their reference station infrastructure,” said Jean-Yves Lauture, product engineer. “With the SXBlue III GNSS, the user doesn’t need to be concerned with their RTK reference station at all. It could be a 20 year-old GPS-only reference station and the SXBlue III GNSS will still create corrections for the GLONASS data and allow you the benefit of GPS/GLONASS RTK productivity in the field.”
By implementing GLONASS, the SXBlue III GNSS immediately increases your RTK productivity with its ability to track 55 satellites (31 GPS, 24 GLONASS). With 12 to 19 satellites in view at all times, the SXBlue III GNSS provides superior performance when working in tough environments such as in and around tree canopy, buildings, and rugged terrain.
The company reports the next-generation SXBlue III GNSS is a small, palm-sized unit that uses a 2.7-inch diameter GNSS antenna. The unit is waterproof (submersible), dustproof, and ruggedized, with an IP-67 rating. Its Class-1 long-range Bluetooth 2.0 has a typical range of 250 meters. The internal, rechargeable, field replaceable Li-Ion battery has on-board LEDs to let the user know how much battery life is left. The operating temperature range of the SXBlue III GNSS is -40°C (-40°F) to 85°C (185°F).
In addition to the built-in long-range Bluetooth transceiver, the SXBlue III GNSS also has a standard DB-9 RS-232 port and a USB Type B port whose outputs are fully programmable up to 10-Hz standard with a 20-Hz option.
The SXBlue III GNSS is targeted at high-precision users in industries such as surveying, GIS, utilities, construction, agriculture, engineering, and other natural resource industries in addition to local, state, and federal government users.
Geneq Inc. has announced the SXBlue II GNSS, a GNSS receiver that uses both GPS and GLONASS with SBAS (WAAS/EGNOS/MSAS/GAGAN) to attain 30-cm/1-foot (RMS) accuracy in real-time using free SBAS corrections. It connects wirelessly to any smartphone, handheld, tablet computer, or notebook computer that is Bluetooth-compliant.
For years, the SXBlue GPS product line has lead the market in squeezing the most out of SBAS for high-precision mapping and surveying users. New technology used in the SXBlue II GNSS allows it to utilize both GPS and GLONASS with SBAS, enabling it to track and use nearly twice as many satellites compared to typical SBAS receiver technology.
“More satellites means more accurate positioning in tougher environments, such as under tree canopy and near buildings,” said Jean-Yves Lauture, product engineer. “GLONASS has proven itself valuable for RTK, and now we are bringing GLONASS to SBAS, with impressive accuracy and tracking results.”
The SXBlue II GNSS builds on the success of the proven SXBlue II GPS that was designed to optimize SBAS performance under tree canopy and in rugged terrain. With the ability to track 55 satellites (31 operational GPS, 24 operational GLONASS), the SXBlue II GNSS uses between 12 and 19 satellites in view at any time, providing superior performance when working under and around tree canopy, buildings, and rugged terrain, Geneq said.
The next-generation SXBlue II GNSS is the same, small, palm-sized unit as the SXBlue II GPS and uses a small 2.7-inch diameter GNSS antenna. The unit is completely waterproof (submersible), dustproof, and ruggedized, with an IP-67 rating. Its Class 1 long-range Bluetooth 2.0 has a typical range of 250 meters. The internal, rechargeable, field replaceable Li-Ion battery has on-board LEDs let the user know how much battery life is left. The operating temperature range of the SXBlue II GNSS is -40°C (-40°F) to 85°C (185°F).
In addition to the built-in long-range Bluetooth transceiver, the SXBlue II GNSS has a standard DE-9 RS-232 port and a USB Type B port with outputs fully programmable up to 10-Hz standard, with a 20-Hz option. Other optional features are L1 RTK for <2-cm real-time accuracy and base station RTCM output.
There is no need for post-processing or other sources of differential corrections as the SXBlue II GNSS uses WAAS (North America), EGNOS (Europe), MSAS (Japan), and GAGAN (India) satellite corrections. Users receive real-time, 30-cm/1-foot positioning all day long, Geneq said.
The SXBlue II GNSS is targeted at GPS/GIS mapping professionals in industries such as forestry, utility, agriculture, and other natural resource industries in addition to local, state, and federal government users.
Geneq will be showing the SXBlue II GNSS at the Esri International User Conference July 24-26 in San Diego, California, booth #1203.
Navilock, a trademark of Tragant Handels- und Beteiligungs GmbH, announces a new family of GLONASS receiver products including the NL-662U USB-based receiver, equipped with a u-blox GLONASS chipset.
Since the end of 2011 the Russian satellite navigation system GLONASS has been available worldwide. Similar in functionality to the US-NAVSTAR GPS system, GLONASS satellites transmit positioning data over distinct frequencies (Frequency Division Multiple Access, or FDMA, versus GPS which uses Code Division Multiple Access, or CDMA).
The new GLONASS receiver products have internal patch antenna in various configurations to serve different installation requirements. Four housing variants with USB or serial MD6/TTL interfaces are available for installation on vehicles or boats.
The u-blox GLONASS chipset features high accuracy to support precision location-based applications such as navigation, datalogging or tracking.
The products provide -158-dBm signal sensitivity with extremely low power consumption to insure reliable performance and long battery life. The u-blox GLONASS chipset facilitates hot starts in less than 3 seconds.
For more information, visit Navilock’s website and click on “new products.”
u-blox, a positioning and wireless semiconductors, announces the acquisition of UK-based Cognovo Ltd., a company specializing in software defined modem (SDM) chip development technology. The acquisition extends u-blox’ chip design capabilities to create differentiated products for strategic markets that require 4G communications combined with global positioning.
“This is a very exciting acquisition for u-blox as it positions us as an agile and cost-effective supplier of high-speed wireless modem products based on our own chip IP. This allows us to meet market demand for connected systems that require positioning, connectivity and application-specific functionality on a single integrated circuit,” said Thomas Seiler, u-blox CEO. “This new foundation broadens our serviceable market, and will increase our margins in the automotive, consumer, and industrial sectors. Our first 4G product is planned for 2013.”
Cognovo’s Software Defined Modem (SDM) technology and development tools quickly translate complex radio modem designs into fully characterized low-power semiconductor chips, u-blox said. The combination of technologies from Cognovo and the recently acquired 4M Wireless will result in a new wireless modem platform based on IP owned by u-blox.
Cognovo has already demonstrated its SDM baseband chip running high-speed 4G cellular functionality working with the LTE protocol stack from 4M Wireless at Mobile World Congress. With these acquisitions, u‑blox lays the groundwork for establishing a leading position in 4G wireless modems similar to the strategy that u-blox followed to become a market leader in GPS/GNSS modules, u-blox said. The market for 4G modems used for machine-to-machine (M2M) applications is predicted to grow rapidly, surpassing 20 million units by 2016.
“We are very pleased to deploy our SDM technology within u-blox,” said Gordon Aspin, Cognovo CEO. “With over 300 man-years of R&D invested in our SDM technology, this acquisition brings together the industry’s most advanced software modem development platform with some of the best IC design and GNSS engineers in the world. This will be an unbeatable team.”
Key terms of the transaction include:
Acquisition of 100% of the shares of Cognovo Ltd at a price of 16.5 million US.
Acquisition of key intellectual property and software.
Integration of the Cognovo business and 30 employees into u-blox’ organization.
Spectra Precision introduced the new ProFlex 800, a GNSS solution with Z-Blade GNSS-centric technology. The ProFlex 800 delivers fast and reliable RTK positioning, even in environments where GNSS signals may be difficult to acquire, Spectra Precision said. Rugged and IP67 rated, the ProFlex 800 is built to withstand harsh operating conditions for a variety of positioning applications.
“The ProFlex 800 is an ideal solution for customers wanting a single GNSS receiver for multiple applications,” said François Erceau, general manager of Trimble’s Spectra Precision, Nikon and Ashtech Business Area. “It offers a unique design with a range of mounting and communications options.”
Used as a backpack rover or reference station, the ProFlex 800 with Z-Blade technology is a flexible GNSS solution for land surveying. Its innovative design also makes it ideal for hard-mounted survey applications such as coastal work, dredging, bathymetry or offshore vessel operations.
The weatherproof, high-impact-resistant molded aluminum housing allows the ProxFlex 800 to operate in harsh conditions.
In addition to a 3.5G internal cellular modem, the ProFlex 800 can use a variety of internal or external UHF modules, providing stable and reliable wireless communications. It can be used as a rover or a base without additional accessories in the field. Its Z-Blade long-range RTK capability combined with industry-leading UHF options help to ensure maximum productivity while in the field.
With its built-in Ethernet capability and embedded web server, users can access the ProFlex 800 from any computer connected to the Internet. This capability allows instant real-time multi-data streaming over an Ethernet connection to build an RTK corrections server without any additional software or equipment, the company said.
Spectra Precision ProFlex 800 CORS Receiver. The Spectra Precision ProFlex 800 is also available as a Continuously Operating Reference Station (CORS). This configuration is an optimal solution when collecting, storing and transferring high-quality GNSS raw data for post processing surveys, geodetic and other applications. Automatic sessions programming, a user-friendly Web-interface, an embedded RINEX converter, FTP push functionality and many other advanced CORS features make the ProFlex 800 CORS a powerful, robust and easy-to-use GNSS solution.
Advanced Ashtech Z-Blade Technology. Z-Blade is a new GNSS centric signal processing technology. Z-Blade uses all of the available satellite signals equally, without preference to any particular satellite constellation, maximizing the user’s ability to obtain reliable GNSS positions in tough conditions. Z-Blade allows users to receive and maintain RTK positioning even if GPS coverage is insufficient. In many work locations, just a few GPS and GLONASS satellites may be visible due to obstacles such as trees or buildings.
The ProFlex 800 is now available through the Spectra Precision global dealer network. For more information visit: www.spectraprecision.com and www.ashtech.com or email: [email protected]
u-blox is launching the u-blox 7, its next-generation core positioning technology platform. Supporting all deployed as well as soon-to-be deployed GNSS, the platform is based on the UBX-G7020 multi-GNSS receiver integrated chip with low power consumption.
With 7 mW power consumption during continuous navigation, u‑blox’ UBX-G7020 is designed for small portable and power-sensitive devices requiring long battery life, high sensitivity, small size, and fast positioning. GPS, GLONASS, Compass, Russian, QZSS, and Galileo satellite positioning systems plus all satellite-based augmentation systems (SBAS) are supported.
“As the satellite systems expand beyond GPS, u-blox 7 is an important step for our customers to design systems that work with all available global navigation standards, particularly GLONASS which is now fully operational. Our multi-GNSS UBX-G7020 integrated circuit does exactly that while achieving two of the most important features that our customers demand: minimum power consumption and small size,” said Andreas Thiel, executive vice president of R&D Hardware and co-founder of u-blox.
The chip has been designed to support the lowest cost stand-alone solution via minimum eBOM; only eight external components are required resulting in a receiver occupying only 30 mm2 on a two-layer PCB. Standard crystal and TCXO are supported. The chip also provides low-power, autonomous log data output of position, velocity, and time. Support for A-GPS and u-blox’ CellLocate hybrid GNSS/cellular positioning technology is embedded to facilitate advanced telematics applications including indoor positioning. Standard and automotive grade are supported.
First samples of the multi-GNSS receiver chip UBX-G7020 are available for customer evaluation. Shortly afterwards, module customers can migrate to the MAX, NEO, and LEA form factors, u-blox’ module series which will all be upgraded to the new u-blox 7 platform.
u-blox 7 maintains software compatibility with u-blox 5 and u-blox 6, and modules provide drop-in compatibility. Both previous generation platforms remain fully supported, the company said. u-blox’ capability of delivering GNSS technology in both integrated circuit and module form provides maximum design flexibility for a wide variety of applications. To evaluate the performance of the u-blox 7 multi-GNSS platform, evaluation kits supporting all u-blox 7 based chips and modules can be ordered.
The European GNSS Agency (GSA) has published its second Global Satellite Navigation System (GNSS) Market Report, providing key information to entrepreneurs in the satellite navigation sector.
GNSS market forecasting is of great interest to private and public GNSS stakeholders, for business and strategic planning and policymaking, according to the GSA. According to the 2012 GSA Market Monitoring Report, the worldwide GNSS market is growing fast and the total market size is expected to increase at an average of 13 percent per year until 2016.
The total enabled GNSS market size is expected to stabilise in the latter half of the decade due to market saturation, price erosion and platform convergence. Global shipments of GNSS devices are lower than previously forecasted up until 2015 yet are forecasted to continue growing to over 1.1 billion units per year.
Expanding coverage. Following up on the first GNSS Market Report published in 2010, the GSA’s 2012 Report includes an analysis of two new sectors: maritime and surveying. Relevant examples from EU research projects have also been included for each sector.
2012 Report Highlights
Road and location-based services (LBS) still in the lead. Road and LBS dominate GNSS device sales (54% and 44% respectively). LBS constitutes 87% of the total GNSS market in terms of units sold and GNSS penetration in smartphones is set to increase from 30% today to almost 100% in 2020. For road navigation, traditional Personal Navigation Devices (PNDs) will gradually disappear from the European market yet remain present in other regions in the form of low cost OEM products. Smartphones and in-vehicle devices will be the preferred means of navigation.
Commercial aviation use will grow. In the Aviation sector, the segment that will see the greatest growth in terms of GNSS equipment revenues will be Commercial Aviation, surpassing general and business aviation by 2018.
GNSS use in agriculture continues to rise. In agriculture the current positive growth trend will continue; low cost precision agriculture solutions based on EGNOS are driving GNSS adoption by farmers in Europe.
Surveying: a growing opportunity. In surveying, the construction segment is dominating the market in terms of units and value. North America is leading in terms of market penetration but the other regions will catch up by 2020 as GNSS is rapidly replacing the traditional surveying and mapping methods in Europe and around the world.
Safer seas with GNSS. In the open sea segment, shipments of search-and-rescue (SAR) beacons will exceed those of other categories making the SAR segment the largest in terms of shipments and second largest in terms of market size.
This month we present a guest column by James D. Litton, who attended the 2012 GPS Partnership Council, jointly sponsored by the Armed Forces Communication and Electronics Association and the U.S. Air Force GPS Directorate. The key topic of this year’s council quickly emerged as the tension between commercial off-the-shelf GPS receivers and official military issue; the two are used side-by-side in active military theaters.
By James D. Litton
This year’s GPS Partnership Council provided among other highlights a discussion of the tensions between commercial off-the-shelf (COTS) receiver systems used in tactical combat operations versus official military GPS user equipment (MGUE), and an enthralling warfighters’ panel that revealed much of those COTS/MGUE dilemmas. The event, held May 1–2 in El Segundo, California, drew an enthusiastic and involved audience, including many GPS veterans. I was struck by the graying of the clan as well as the practiced and confident presentations of current civilian and military program staffs.
Keynote speaker Brig Gen Martin Whelan, Director of Requirements, Headquarters Air Force Space Command, emphasized that ideas for improvement of the system would be hard sells under current budget realities, but good ideas for lower cost would be welcome. Referring to the three segments — space, ground, and user — he recommended that the segments should talk with each other and challenge requirements. In effect, he implied that the separate segments could reduce overall costs, rationalize requirements, and cooperate better in optimizing the resilience and flexibility of the system, including — this is my interpretation — taking advantage of the “competitive” GNSSs to effect user satisfaction.
According to Whelan, resiliency of the space segment is a top priority; smaller satellites, hosted payloads, and net-centric designs were highlighted. He commented that multiple GNSSs should be employed in such a way that the user does not know the difference.
Regarding the upcoming budget, he told us that Department of Defense will be cut by 22 percent, the Air Force will drop 9 percent — but the AF space budget only 1.5 percent. A notable exception to the generally favorable overview was his comment that the MGUE segment, from a distance, looked uncoordinated. Much more along this line came up later during both days of the Council.
Widespread COTS. There was an air of defensiveness about the user segment, and many comments on both the success and the risks associated with the widespread use of COTS user equipment. We heard further commentary on the very infrequent use of SAASM keys, due to the difficulty of procedures to obtain and employ them, and due to the perception of very low risk of jamming and spoofing threats in current combat deployments.
A session on “The Future Military Receiver” enlisted two panels of government experts and contractors from Deere-NavCom, Garmin, IEC, Johns Hopkins Applied Physics Labs, Raytheon, and Rockwell-Collins. Although the unclassified nature of the presentations limited the level of detail, it clearly emerged that many tactical, in-combat deployments of COTS GPS receiver systems had occurred and continue to occur.
A video compared the jamming resistance of a Garmin receiver with that of approved GPS User equipment receivers. It showed a screen of the Garmin receiver losing satellites at greater distances from the jammer and losing lock at closer distances. Directorate employees and officers made several references to the risks from dependence upon COTS receivers, and related with considerable candor the difficulties with large, expensive, power-hungry MGUE, both mobile and platform-mounted, models of which were held up during the presentations — often to laughter from some in the audience.
More on this followed in Day Two’s dramatic warfighters’ panel, which many people felt was by itself worth the price of admission. These experienced users of GPS under fire — from Coast Guard search and rescue to Air Force forward controllers calling in air strikes within range of small-arms fire — related direct personal experience in a broad array of critical applications. They clearly knew how to use COTS equipment to good advantage and described the operational protocols developed from hard and sometimes painful experience.
Manipulation of multiple screens in a heavy device, which requires initialization or synchronization before dismounting, was often simply not an option. Translation of such experience into qualified requirements is a major challenge for the Air Force and Army. Overdependence on the anecdotal but very valid combat experiences would weaken a design against an enemy with even rudimentary jamming and spoofing capability.
An astute questioner asked “Have you seen any evidence that the enemy (in Afghanistan) has changed tactics because of our technology?”
The answer came “Not yet,” with a comment that the enemy’s early warning systems are very sophisticated and the target of a mission to capture a high-value individual (HVI) frequently knows that such a mission is underway; his support network spirits him away and attacks the mission with the advantage of surprise denied to our forces, abetted by the advantage of favorable terrain and numbers accruing to the enemy.
The Puck. The Army-led MGUE program status was described as being at technology readiness level (TRL) 6.0; the request for proposals was released on April 16. The key to the success across platforms of this “system of systems” was said to be the Common GPS Module (CGM), also referred to as the Puck. This module is M, P, and C/A code-capable and SAASM-capable but has flexible interfaces and “emulates commercial.” The module itself is a system-on-chip (SoC) that can be integrated across many platforms. Depending upon the level of integration employed, it can be as small as chips found in smartphones or somewhat larger.
The program schedule was defended as having only been funded two years ago and having very complex security and platform interfaces. This program presentation drew a large number of questions and commentary from the audience, much of it politely skeptical and showing impatience with the bureaucratic aspects of the program. Well-informed former military field-grade officers in the audience questioned its real availability. The answer that it would be available in quantity sometime in 2017 did not please the questioners.
In short, procurement regulations appeared to be the highest barrier to a rapid, flexible program for a net-centric, open-architecture system development.
Currently, the circuit boards for the MGUE are classified secret, but it is hoped to have these at a confidential or unclassified level for deployment by handling the encryption exclusively in software. The leader of this presentation indicated that software receivers were the ideal but were not available, so reduction in size, power consumption, and complexity in hardware was the goal.
Trumping Military. One almost nostalgic comment hearkened back to the time when military systems were regarded as the height of technological excellence, whereas it is now generally perceived that commercial systems trump the military in sophistication. Garmin claimed to have developed SAASM receivers in the lab but found little interest from business leaders at that time.
The CEO of Mayflower Communications, which makes and sells miniaturized SAASM receivers, pointed out that anybody could make a SAASM receiver employing a Sandia crypto-chip approved by the U.S. National Security Agency (NSA) but pointed out, as did several others, that the availability of certifications and authorizations was very limited, and that volume drove cost. Implicitly, NSA’s requirements and protocols got blamed for the limited distribution and use of SAASM receivers.
Day Two
The second day of the GPS Partnership Council comprised The Nation and The Warfighter. In the latter group came an outline of the Army’s COTS vision and — the hit of the entire conference — the Warfighter panel with a keynote introduction by a USAF colonel warrior now at the GPS Directorate.
The Nation. Tony Russo, director of the National Coordination Office for Space-Based Positioning, Navigation, and Timing, disabused those who thought that the apparent demise of the LightSquared threat had eliminated that subject from his agendas; he still deals with it often. He provided entertaining and informative examples of non-obvious and valuable applications of GPS, from assessing rugby players’ game performance through detection of clandestine underground nuclear tests to a social application of matching available part-time and temporary workers with jobs when labor demand surges and a roster shows where the closest qualified candidates are.
John Merrill of the Department of Homeland Security (DHS) identified 18 critical infrastructures that depend upon GPS integrity and showed the cascading effect of taking out sites like SCADA (Supervisory Control and Data Acquisition) systems. He related a threat-illustrative story of a DHS agent who required constant contact via his agency smart phone but who could not get reception while attending mass in church. The pastor later and very proudly showed him the mobile phone jammer in the sacristy; he had given up on asking parishioners to turn off their cell phones off during services.
James Miller of the National Aeronautics and Space administration noted that only 5 percent of space missions lie outside the GPS coverage envelope (3,000 kilometers to geostationary altitude of 35,800 kilometers is the space service volume). Reducing the burden on spacecraft tracking networks is a highly profitable application for GPS.
Warfighters Panel. These real-life experiences from combat and other vital operations could easily justify an entire article of their own. The following examples will illustrate the life-saving force multiplication of GPS, particularly the ubiquitous civil GPS technology in the current combat environment.
• An Air Force Special Operations Major described a mission to snatch an HVI, giving great detail on battlefield terrain, combat conditions, and how he worked between a COTS GPS receiver and a COTS handheld computer with Google Earth-like facilities to bring JDAMs (GPS-equipped smart munitions) onto an ambush mounted by defenders of the HVI, who were alerted to the raid by their extensive and sophisticated early-warning network consisting of sympathizers with cell phones. His description of the heroics of individual forward controllers, their injuries and fatalities, and the symbiosis of man and machine in a relatively benign electromagnetic interference but relatively malign electromagnetic propagation environment, and overtly and covertly hostile indigenous population, was dramatic and compelling.
Clearly, unsophisticated and easily-available high-power jammers rapidly alter such situations to reduce our technological advantages. Also clear was the need to design user equipment, not just to reject interference but to minimize time and the inevitable ambiguities in actual combat situations.
• A Coast Guard lieutenant described the search-and-rescue missions he flies out of local airports to Pacific Ocean sites. Again, COTS equipment, aided by the near-ubiquity of commercial GPS equipment, along with VHF marine radio on boats and ships, enhances these mission results over those flown with standard USCG-issued navigation equipment.
• An Air Force tanker pilot major now attached to the GPS Directorate described three personal experiences. He once had to ask his boom operator to retrieve the Garmin receiver issued in the survival kit in order to navigate the tanker for rendezvous with tactical aircraft needing fuel when the tanker’s standard equipment failed.
When tasked to fly into an airport in Afghanistan with unreliable navaids, under suddenly occurring zero-zero conditions, the onboard GPS enabled him to land safely.
In a third instance in Iraq, he observed a downed airman being approached by gunmen. The gunmen with AK-47s were being targeted by drone operators. The major was able to discern that these gunmen were friendly forces moving to rescue the downed airman and avert a friendly-fire disaster. The downed airman’s ability to send his exact coordinates were key to the ability of the observer to get close enough to direct rescue efforts and to avoid a fatal error.
• A Navy surface warfare lieutenant commander and a CWO Riverine or small boat skipper cited instances in which GPS was essential to missions and ways in which user equipment design could improve their operations — for example, by making it float.
All the veterans repeated, during or after their accounts of ways in which GPS saved lives or enabled missions, “thank you for what you do,” addressed to the audience, the presenters, and their leaders. Going into denied territory places a high premium on user friendliness, battery life, robustness, size, and weight. In the future, inevitably, jam and spoof resistance will be an object of gratitude, as well.
Final Review. We all know these things, intuitively and by doctrine, but hearing reports from people in harm’s way or retrieving comrades from harm’s way was a great addition to the usual program and technology descriptions by the development teams.
I was particularly impressed with the very articulate, sophisticated, and focused presentations of these combat veterans. It is highly incumbent on the industry and the government GNSS leaders to translate these experiences into design requirements quickly, so that future systems are less dependent on individual ingenuity and on commercial gap-fillers.
Much of this progress depends on truly incorporating the applications focus of commercial product development and on use of other GNSS systems for robustness, flexibility, and affordability — often quoted as mission goals by the leaders of this enterprise.
Trimble introduced today the next-generation of its Trimble GPS Pathfinder family — the Trimble Pro 6H and Pro 6T receivers for GIS and mobile mapping. The Trimble Pro series with advanced features allows mobile workers to configure a solution for a wide range of applications, delivering flexibility in professional GIS data collection, Trimble said. The series offers a new streamlined form-factor and dramatic productivity improvements in difficult GNSS environments with Trimble Floodlight technology.
The modular Trimble Pro series receiver gives users the flexibility to choose their setup configurations:
Optimized for use with Trimble data collection devices such as the Trimble Juno or Nomad G series handhelds, or Yuma tablet computer, the Trimble Pro series can also be used with other tablets and handhelds with NMEA output.
Real-time or postprocessed GIS workflows.
The receiver can be deployed in a backpack, on a pole or mounted on a vehicle.
Two models are available: the Trimble Pro 6H delivers decimeter accuracy, while the Pro 6T is the submeter model for standard GIS applications.
With the availability of the new Pro series receivers, data collection professionals now have access to the productivity-enhancements of Floodlight technology in both integrated and modular configurations,” said Daniel Wallace, general manager of Trimble’s GIS Data Collection Division. “While some prefer the convenience of an integrated, all-in-one handheld, others will appreciate the Pro series’ flexibility to choose from a range of data collection devices such as a high-resolution tablet or lightweight Trimble Juno.”
Trimble Floodlight technology allows users to collect decimeter accuracy data in tough GNSS environments, Trimble said. Buildings and trees can cause satellite shadow and limit the environments where high-accuracy GNSS data collection can be performed. Trimble Floodlight technology combines a range of techniques to increase the availability of positions and boost accuracy in areas affected by satellite shadow. Using Floodlight technology, the Pro series can keep teams productive without compromising on accuracy. Users can work with fewer disruptions and ensure better data, faster data collection and higher field efficiency.
Trimble Pro series receivers are rugged and built to withstand the rigors of long hours in tough outdoor conditions, yet optimized for high-accuracy GIS data collection workflows, Trimble said. For applications such as utilities inspections and timber stand valuations, Trimble Pro receivers provide long battery life and tough construction for dependable service over the course of rigorous data-collection projects.
With its IP65 rating, the receivers offer reliable operation, even after prolonged exposure to water and dust, Trimble said. An integrated antenna reduces the complexity of the system for fast setup and swift data collection campaigns. Field workers can be up and running with minimal training, saving time and money. Combined with a Trimble handheld solution and Trimble TerraSync software, the complete system provides dedicated field workflows to simplify data collection and improve integration with the GIS for total workflow improvements.
The new Trimble Pro 6H and 6T receivers are available from Trimble’s worldwide Mapping & GIS authorized distribution channel.
