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In the world of global navigation satellite systems (GNSS), there are five key watchwords: accuracy, integrity, availability, continuity and coverage. While all five of those parameters are very important, their priority order depends on the application.

Accuracy: how well a measured or estimated position or time conforms with its true value. If you are a surveyor, accuracy and integrity are your biggest concerns.

Integrity: how much the information supplied by the system can be trusted to be correct. This requires the system to provide timely warnings to the user when the equipment is unreliable for navigation purposes—due to obstructions, jamming, multipath or any other event that degrades accuracy.

Availability: the percentage of time that a signal is available to the user. For location-based services, this and coverage are probably the most important parameters.

Continuity: the ability of the total navigation system to continue to perform its function during the intended operation. Continuity is critical whenever reliance on a particular system is high. For a pilot during an instrument approach procedure, continuity and integrity are vital.

Coverage: the area over which a signal is required. For farmers, it is their fields, for ships, the world’s oceans.

In our October 2021 issue, we celebrated the availability of four global navigation satellite system (GNSS) constellations. Below is the status (as of Feb. 23, 2023) of these four GNSS and their two regional cousins.

Many thanks to Mohamed Tamazin, Ph.D., Senior GNSS Architect for GNSS Simulation with Orolia — a Safran Electronics & Defense company, who provided or confirmed these data. While the data on GPS and Galileo are easily accessible, those for the other constellations are difficult, in some cases very difficult, to find.

— Matteo Luccio, Editor-in-Chief

Inertial Labs has released its third generation of MEMS sensor-based inertial measurement units (IMU), MEMS KERNEL-210 and KERNEL-220.

The KERNEL-210 and KERNEL-220 are compact, self-contained, strapdown, tactical-grade IMUs that measure linear accelerations and angular rates using their aligned and calibrated three-axis MEMS accelerometers and three-axis MEMS gyroscopes.

Angular rates and accelerations are determined with low noise and good repeatability for both motionless and dynamic applications.

The KERNEL-220 model utilizes accelerometers with ±40g and ±90g measurement ranges. The IMU is fully calibrated, temperature compensated and mathematically aligned to an orthogonal coordinate system. The KERNEL-220 contains gyroscopes with a bias in-run stability of less than 1 deg/hr and accelerometers with an in-run stability bias of 0.005 mg.

Fairview Microwave has introduced a new series of mil-spec GPS/GNSS antennas for mobile and small form factor applications.

The MIL-STD-810G GPS/GNSS antennas include multi-standard GPS L1, Galileo E1 and GLONASS options and are designed for environmental performance according to the MIL-STD-810G standard.

The antennas are available in passive and active versions and provide coverage from 1,597 MHz to 1,607 MHz. The MIL-STD-810G GPS/GNSS antennas feature linear polarization for cross-polarized isolation, nominal gain options of -3 dBic and 10 dBic, and SMA mounts.

The mil-spec GPS/GNSS antennas are IP67-rated.

Fairview’s mil-spec GPS/GNSS antennas are available now.

Geographical information of urban areas is critical because it forms the basis for planning, intelligent urban modeling and disaster mapping and management. For many decades, ground surveys and aerial photographs were used as the primary tools for collecting this data. Starting in the 1990s, these methods were replaced by such advanced remote-sensing technologies as synthetic aperture radar (SAR) and ground-based interferometric radar (GBIR).
This article explores the use of software-defined radio (SDR) platforms for acquiring high-resolution SAR/GBIR images, including:

• How low-cost commercial-off-the-shelf SDR platforms can be used to realize complex systems for acquiring images and processing measurements.
• How different specifications of SDRs make them suitable for use in SAR applications.

Hazard Monitoring in Urban Areas

Many urban areas and critical infrastructure are in regions highly prone to natural disasters such as volcano eruptions, earthquakes, avalanches and landslides, or near man-made systems such as dams and quarries. Monitoring of surface changes and structures is integral to the mitigation of risk and ensuring public safety. Modern remote-monitoring systems allow surface displacements to be monitored without the need to access a location. With these systems, several square kilometers of Earth’s surface can be monitored at once and with high accuracy. The sub-millimeter accuracy of modern remote-monitoring technologies enables accurate measurements to be collected with impressive precision, including in rainy and foggy conditions.

Remote-monitoring systems are autonomous and can operate for a long time without human intervention. Their real-time feedback makes them suitable for use as early-warning systems. In addition, these monitoring systems can be integrated into a wide range of sub-systems, such as decision support systems that assist decision makers in assessing emergency plans and selecting the best options.

Using Radar to Measure

Details of the surface observed by a SAR satellite are encoded in the amplitude and phase of a SAR image. The amplitude component contains information about the surface roughness and terrain slope of the target area, while the phase component contains information about the elevation of the satellite.
A typical SAR satellite transmits microwave signals toward a target area at an oblique angle and measures the backscattered signal. The intensity of the reflected signal is mainly determined by the roughness and the structure of the target, and the distance between the satellite and the target. This measurement is usually described in terms of the radar cross-section (RCS) parameter, which is obtained by calculating the ratio of the scattered to the intercepted signals as shown in this equation:

The RCS parameter is mainly dependent on the surface roughness and the dielectric properties of the target object.
The interferometric SAR (InSAR) technique allows surface movements to be identified. These observations also can be used to measure and monitor changes associated with volcanic eruptions, tectonic activity and other geophysical processes. To identify crustal changes using this geodetic technique, at least two SAR images are required.

In differential InSAR, two images of the same location that are recorded at different times are used. If a surface movement has occurred between the first and the second acquisition, a phase shift is observed (Figure 1). The presence of interference fringes on an interferogram is an indicator of a phase shift and these fringes are summed during processing to provide a relative value of the phase change.

Ground-based SAR (GBSAR) employs the synthetic aperture radar technique to capture high-resolution images of the electromagnetic reflectivity of a target. This remote-sensing system is commonly used for monitoring civil infrastructure, buildings, mines, landslides, glaciers and more. While spaceborne SAR is capable of surveying large areas and records data over long periods of time, usually several weeks or months, GBSAR is suitable for monitoring small areas and has short sampling periods, usually a few minutes. In most surveying applications, the two remote-monitoring techniques are used together in a complementary fashion to enhance the overall performance.

The all-weather monitoring capability of satellite-based SAR makes it a popular tool for natural disaster management. Since the launch of the first SAR satellite in 1991, this technology has provided many emergency response teams with important insights on manmade and natural hazards. SAR data can be used to study different aspects of long-term behaviors of slow-moving surfaces, which is critical for planning emergency response to natural hazards such as volcanic eruptions, landslides and avalanches. SAR satellites orbit Earth at altitudes of between 500 km and 800 km and operate in the C-band (5 GHz to 6 GHz), X-band (8 GHz to 12 GHz) and L-band (1 GHz to 2 GHz). The temporal resolution of these satellites is mainly determined by their revisit periods.

Software-Defined Radio Platforms

A typical SDR platform features a radio front end (RFE) and a digital back end, with the RFE performing receive (Rx) and transmit (Tx) functions and offering a wide tuning range, typically 0 GHz to 18 GHz. This range is acceptable for widely used bands in SAR applications, including L-band, C-band and X-band.

The digital back end of a high-performance SDR system features a field programmable gate array (FPGA). This FPGA offers a variety of digital signal processing (DSP) capabilities, including upconverting, downconverting, modulation and demodulation. In addition, an SDR platform offers multiple transmit and receive channels, making it suitable for implementing multi-in multi-out (MIMO) radar systems.

The architecture of SDR platforms allows them to integrate easily with a wide range of complex systems, such as SAR systems. The reconfigurability of SDRs allows upgrades and updates to be implemented without modifying the existing hardware, and can be designed to meet the size, weight and power (SWaP) requirements of an application. These features make SDRs suitable for implementing custom SAR monitoring solutions in small and large ground stations (Figure 2).

Integrating SDRs with SAR

A software-defined radar (SDRadar) is an SDR-based radar system that offers high flexibility and robustness. Compared to conventional radar, SDRadar offers many benefits, including the opportunity to reuse hardware, develop multi-function radar solutions, achieve faster development cycles, and have easier implementation of updates and new algorithms.

Tests with prototype SDR-based GBSAR systems have revealed the strong potential of SDR-based implementations. The MIMO architecture of an SDR platform allows realization of complex multi-frequency GBSAR systems uniquely suited for measuring displacement and other geophysical characteristics of landforms. SDR-based GBSAR systems can operate in different frequency bands and offer unmatched flexibility when it comes to signal generation and digital signal processing.

Many prototypes of airborne/satellite SAR systems based on SDR platforms have been implemented and their performance evaluated. Results have shown that they can offer better performance compared to conventional implementations. The use of multiple independent channels by SDR platforms allows the realization of compact and power-efficient multimode SAR systems, while the architecture of an SDR platform allows complex signal processing techniques such as digital beamforming (DBF), null steering and direction of arrival estimation to be implemented on FPGA.

Benefits of Integrating SDRs with SAR Solutions

Integrating SDRs into SAR systems provides many benefits. The MIMO architecture of SDR systems provides more channels than are required for SAR functions. The extra channels can be used for other applications such as satellite communications during emergencies. The wide frequency-tuning range of an SDR system allows the realization of a multi-function system with applications using different frequency bands. The reconfigurability of SDR platforms allows them to be repurposed for other applications. In addition, this reconfigurability enhances reusability, scalability and power efficiency. The low-latency FPGAs in high-performance SDR systems allow the realization of ultra-high-speed DSP algorithms for use in image processing and DBF.

Conclusion

The reconfigurability and impressive performance features of SDR platforms make them ideal for implementing scalable and flexible SAR monitoring systems for measuring land changes. The wide tuning range and MIMO architecture of SDR devices allows realization of a multi-function and multi-frequency system using a single device. In addition, the reconfigurability of SDR devices allows hardware reuse and low-cost implementation of updates and new algorithms.

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Brendon McHugh is the field application engineer and technical writer at Per Vices. He possesses a degree in theoretical and mathematical physics from the University of Toronto.

Simon Ndiritu is an independent technical writer for Per Vices with a background in electrical and electronic engineer with a wealth of experience in designing hardware and firmware. He also has a passion for writing.

U-blox has signed an agreement with GMV to combine GNSS receiver hardware from u-blox with GMV’s safe correction service and sensor fusion and positioning engine. This solution is suitable for automotive applications because it provides a holistic safety approach that maximizes performance and minimizes timetomarket costs.

Starting in April 2023, u-blox will directly commercialize the solution. This includes integration services and certification support provided jointly by u-blox and GMV for applications such as ADAS Level 2+ and vehicle autonomy.

The collaboration was forged at the recent Mobile World Congress (MWC), Barcelona 2023. The two companies will work hand in hand to integrate their technologies and provide a solution for the needs of future automotive application

VOTIX has partnered with Iris Automation to enable safe beyond visual line of sight (BVLOS) flights by integrating Iris Automation’s Casia G ground-based detect and alert system into the VOTIX cloud-based UAV operating system.

This integration makes remote operations a reality for enterprises that need effective and flexible UAV BVLOS deployments, from routine automated inspections of critical infrastructure to rapid mobilization seen in UAV as first responder programs.

This hardware-software solution will feed data from the Casia G system into the VOTIX platform to provide a complete picture of the operational airspace in real-time.

The Casia G system can detect non-cooperative or intruder aircraft at a distance by monitoring the airspace and providing their precise location and classification data. This enabes automated conflict resolution via the VOTIX platform.

“Our mission is to make BVLOS easy,” said Ed Boucas, VOTIX CEO. “We have integrated every aspect of drone operation in a single pane of glass so that pilots can easily perform safe and secure BVLOS flights.”

M3 Systems has played an important role in the CPS4EU European project by providing use cases and solutions centered around the company’s GNSS simulator, StellaNGC.

The project aims to develop new Cyber-Physical Systems (CPS) technologies that will improve the efficiency and reliability of critical infrastructures, such as transportation systems, energy networks and communication systems.

The CPS4EU project involves 36 partners from various European countries, including M3 Systems, working to develop new standards and guidelines for the design, deployment and operation of CPS.

The M3 Systems’ flagship product was integrated into a new test bench, to be used by position systems, to assess reliability for autonomous driving and intelligent mobility applications.

In July 2020, my First Fix article discussed the Geodesy Crisis in the United States. In January 2022, Mike Bevis, collaborating with others, prepared a white paper titled “The Geodesy Crisis,” documenting the concern about the lack of trained geodesists in the United States. Since then, my November 2022 survey scene column highlighted that without investment in geodesy, the United States will not have the available skills and knowledge to develop new geodetic technologies and improve models to address challenges to society. In December 2022, Matteo Luccio discussed the urgent need for U.S. geodesists with Everett Hinkley, who works for the federal government, serves as a subject-matter expert on several high-level boards, and dubs himself a “concerned citizen geodesist.”

Well, things are starting to happen. NGS is soliciting grant proposals from eligible organizations to implement activities that modernize and improve the National Spatial Reference System (NSRS) and advance the science of geodesy in the United States. See the image below.

I realize that this is very short notice, but all Letters of Intent (LOIs) must be received no later than Wednesday, March 22, 2023. Full proposals do not have to be completed until April 24, 2023. The grant information and related material can be found here.

This is a great opportunity for institutions of higher education, state, local and Indian tribal governments to partner with industry and private consultants to advance the science of geodesy.

NGS Geospatial Grant Opportunity: https://content.govdelivery.com.

A roundup of recent products in the GNSS and inertial positioning industry from the March 2023 issue of GPS World magazine.

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UAV

Anti-Jamming Device
Provides protection from three directions of attack 

The GPSdome 2 is tailored to defend small- to medium-sized tactical UAVs as well as manned and unmanned ground vehicles. With a small form factor (500 g, 87 mm x 91 mm x 61.55 mm) and minimal power consumption, GPSdome 2 is suitable for loitering munitions as well as UAVs. Fully retrofit and completely standalone, the system is compatible with almost any off-the-shelf GNSS receiver as well as standard active GNSS antennas, meaning that it can be integrated into existing GPS systems or into new product lines, manned or unmanned. With sophisticated algorithms and a proprietary RFIC, GPSdome 2 analyzes RF interference in the environment and combines multiple antenna patterns to create and dynamically steer three nulls in the direction of any hostile signal. GPSdome 2 provides simultaneous dual-frequency protection (GPS L1 + L2 or GPS L1 + GLONASS G1), creating up to three nulls, protecting from three jamming directions within each band in real time, making it suitable for PNT applications. The GPSdome 2 is a dual-use, non-ITAR device and comes with optional mil-spec compliance.
InfiniDome, infinidome.com

Command and Control
Designed for easy integration

The SkyLine C2 management platform and muLTElink airborne radio systems (ARS) are designed to integrate, which enables a self-healing command-and-control network capable of both path and link diversity. This eliminates lost-link possibilities over broad terrain and altitude ranges. MuLTElink ARS consists of two models — muLTElink915 and muLTElink5060, the core of the uAvionix C2 system. The muLTElink915 model combines globally licensed aviation LTE, enhanced with frequency hopping 902 MHz – 928 MHz industrial, scientific and medical frequencies capability. The muLTElink5060 model combines global LTE with aviation-protected 5,030 MHz – 5,091 MHz C-band. Each muLTElink model allows up to one external CNPC radio to be optionally connected to allow simultaneous use of all three frequency ranges, higher power C-band operation or future radio integrations.
uAvionix, uAvionix.com 

VTOL UAV
With Sony a7R mark III and IV camera 

Atmos has integrated the Sony a7R mark III and IV cameras into its vertical take-off and landing (VTOL) fixed-wing UAV, the Marlyn Cobalt. This will increase coverage and accuracy achieved in a single flight for surveyors. Both cameras have an ISO of 32,000, which is expandable to 102,400, and camera sensors with high megapixel count — 42,4 MP for the a7R III and 61 MP for the a7R IV. When combined with Zeiss’ 35 mm and 21 mm lenses, it enables UAV surveyors to achieve ground sample distance levels below one 1 cm. The integration of the two cameras enables Marlyn Cobalt users to map an area of 210 ha with centimeter-level accuracy in a single flight.
Atmos, atmosuav.com

UAV and Lidar Systems
Suitable for geospatial professionals 

TrueView 535 consists of updated lidar sensors, adding a third return, increasing mapping abilities below canopy. An additional third nadir camera offers another point of view and improves photogrammetry quality. It also includes a longer, usable lidar range to increase flexibility. TrueView 720 is a fourth-generation Riegl VUX-120 with three laser beam orientations. It provides high-point density corridor mapping. Using the Riegl VUX-120 with three laser beam orientations (nadir, +10 degrees forward and –10 degrees backward) and three oblique/nadir cameras enables data collection from more surfaces in one flight path. One application of TrueView 720 is scanning power lines. Users can capture the poles vertically, front and back. The extreme range of this system means it can be integrated with UAVs, airplanes or helicopters. In addition to the two sensor payloads, GeoCue has launched its LP360 software add-on for processing and visualization — the 3D Accuracy and the Accuracy Star hardware.
GeoCue, geocue.com

OEM

Voltage Regulator
Device for LEO space application

The MIC69303RT is a radiation-tolerant power management device for space application developers. It is a high-current, low-voltage device targeting low-Earth orbit space applications. The MIC69303RT operates from a single low-voltage supply of 1.65 v to 5.5 v and can supply output voltages as low as 0.5 v at high currents. It offers high-precision and low dropout voltages of 500 mv under extreme conditions. The MIC69303RT is a companion power source solution for microcontrollers, such as the SAM71Q21RT and PolarFire field-programmable gate arrays. MIC69303RT is designed for harsh aerospace applications and remains operational in temperature ranges from -55 C to +125 C.
Microchip Technology, microchip.com

LEO Satellite Device
Designed for GNSS/PNT lab testing

SimORBIT, a low-Earth-orbit (LEO) satellite solution software, contains a space-borne receiver developed by SpacePNT. The software is designed to aid developers in determining LEO orbits more accurately for GNSS/PNT lab testing. SimORBIT calculates LEO orbits as well as their environments and intricate characteristics to provide an accurate result to developers for testing. The software replicates LEO orbits so that simulations can provide the realistic environment of a LEO satellite, including gravitational and atmospheric impacts the satellite could encounter in space. Developers can create non-ICD signals via I/Q injection, or by the “Flex” feature, generating space-centered PNT signals to be developed in the lab as realistically as possible.
Spirent Communications, spirent.com

5G Chipset
Includes GNSS 

The ALT1350 implements GNSS, cellular and Wi-Fi-based location in a single chipset. The cellular LTE-M/NB-IoT chipset is designed to enable additional low-power, wide-area (LPWA) communication protocols; intermittent LTE and GNSS (GPS/GLONASS) navigation for low-cost applications; and concurrent LTE and L1/L5 GNSS for tracking applications. The ALT1350 incorporates a sensor hub to collect data from the sensors while maintaining ultra-low power consumption. It also provides cellular and Wi-Fi-based positioning and is tightly integrated to provide power-optimized concurrent LTE and GNSS to accommodate various tracking applications, which can be demanding with a single chip. The chip is designed to enable deployments for the internet of things (IoT), including location technologies.
Sony, altair.sony-semicon.com

Embedded Antenna
Supports multiple satellite constellations

The ANT-GNL1-nSP is a surface-mount embedded GNSS antenna supporting GPS, Galileo, GLONASS, BeiDou and QZSS in the L1/E1/B1 bands. The ANT-GNL1-nSP antenna exhibits high performance in a compact size (10 mm x 8 mm x 1 mm) and features linear polarization and an omnidirectional radiation pattern. The antenna is available in tape and reel packaging and is designed for reflow-solder mounting directly to a printed circuit board for high-volume applications.
Linx Technologies, linxtechnologies.com

GNSS Module
Based on a MediaTek chipset

The ORG4600-MK01 dual-frequency module provides higher precision than the company’s previous modules. It has sub-1 m precision at a cost lower than that of the company’s first L1+L5 module, the ORG4600-B01, which is based on Broadcom’s chipset. The 10 mm x 10 mm ORG4600-MK01 was designed for applications deployed in challenging environmental conditions. The solution also includes RTCM, a logger and accurate orbit prediction.
OriginGPS, origingps.com

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MAPPING

Navigation Software
Includes enhancements to existing software and more

Navigation software development kit version 2.9 provides pre-built applications compatible with Android and IOS. SDK v2.9 provides the primary navigation components across a workflow using lines of code instead of starting from square one. The drop-in user interface is customizable to reflect a developer’s brand, obviating the need to manually develop a full end-to-end application. Navigation SDK Copilot — a backend analytics tool for CX on navigation applications — collects trace files of navigation sessions and search analytics data from users. Developers can use this data to gather feedback and collective user data to create touch points with users and improve application experience based on their data-drawn conclusions. Matrix API has been updated to support scheduled departure times and provide optimal driving routes, creating a more accurate estimated time of arrival.
Mapbox, mapbox.com

Defense Platform
For developing Android applications 

LuciadCPillar is designed for the development of mobile applications for dismounted soldiers in the field. Developers can build applications with 2D and 3D views. It features military symbology and supports many geospatial data types including vector data, raster data, elevation data, point clouds and 3D meshes. It has the same capabilities found in desktops, in-vehicle and browser applications built with LuciadLightspeed, LuciadCPillar and LuciadRIA. The platform offers capabilities to match high-resolution screens, graphic processing units and multi-core processors including the ability to display 3D data in mobile applications. LuciadCPillar supports ARM processors and an application programming interface, which aligns with the Android developer experience. Impact, a French system integrator, partnered with Hexagon to test LuciadCPillar and will integrate it into its Delta Suite product, which is used by the French Special Operations Command. LuciadCPillar is part of Luciad 2022.1, which is available now globally.
Hexagon, hexagon.com

Surface Mapping
Designed for 3D surface mapping 

The Surfer package is designed for 3D surface mapping and provides robust subsurface visualization and modeling functionality by incorporating many true 3D gridding and visualization tools. With the enhanced functionality, users can now model an additional variable, a C variable, such as a contaminant or chemical concentration, along with the traditional X, Y, Z values. Surfer also includes the ability to create a 2D map of a slice-through 3D grid, which users can move up and down through the grid, illustrating how the C value changes with depth. Part of Surfer’s enhancements is isosurface creation, enabling visualization of the 3D grid in the 3D view as an isosurface, providing another way to see how C data varies with depth or elevation. The new 3D-rendered volume functionality also allows users to visualize the 3D grid in the 3D view as a solid body by assigning colors to different C values, highlighting variations in the data.
Golden Software, goldensoftware.com