“Seen & Heard” is a monthly feature of GPS World magazine, traveling the world to capture interesting and unusual news stories involving the GNSS/PNT industry.
West Point Cadets Map Electronic Warfare West Point cadets conducted a senior thesis project investigating the use of GNSS technology to map and visualize electronic warfare activities in the South Pacific, specifically focusing on GNSS spoofing. Their research, centered on the Huangpu River and Northeastern Shanghai, aimed to identify patterns of malicious GNSS interference and potential perpetrators, highlighting the strategic and economic motivations behind these actions in the region. By developing data visualizations of spoofing incidents, the cadets created a model that could be scaled up to analyze larger areas.
Credit: Eric S. Bartelt / USMA PAO-VI
South Africa Rising Above Water Researchers from the University of Bonn have found that South Africa’s land is rising by up to 2 mm per year, not because of deep mantle activity, but due to water loss from severe droughts. This uplift was detected using the TrigNet network of GNSS stations, which precisely measures changes in land elevation. As groundwater is depleted, the Earth’s crust rebounds upward — a process GNSS stations can monitor in real time.
Credit: THEGIFT777 / E+ / Getty Images
Türkiye to Launch Homegrown Satellite Navigation and Mapping System Türkiye is developing the Regional Positioning and Timing System (BKZS) to launch its own GPS and mapping application, in an effort to reduce dependence on foreign technology and enhance cybersecurity amid growing industrial automation. The system will provide precise location, navigation and timing data via Turkish satellites as an alternative to global systems including GPS, supporting critical sectors such as military operations, civilian communications, smart transportation, and precision agriculture.
Quantum Navigation System Serves as GPS Backup Q-CTRL, a quantum infrastructure software company based in Sydney, Australia, has demonstrated a new quantum navigation system, Ironstone Opal, as a backup to GPS technology. The Ironstone Opal system uses quantum sensors to detect variations in the Earth’s magnetic field, determining precise geographic coordinates with the help of artificial intelligence-based software. Ironstone Opal is passive and does not emit signals, making it resistant to detection and jamming. Field trials showed the system outperformed a high-end inertial navigation system and served as a reliable GPS backup by up to 50 times in ground vehicles and 11 times in aircraft.
The Turkish Armed Forces have added the BAHA autonomous sub-cloud UAV to their reconnaissance capabilities. The UAV can be used for tracking, detection, area protection, intelligence and electronic warfare.
The BAHA, developed by Turkish defense company HAVELSAN, is an independent sub-cloud UAV equipped with vertical take-off and landing (VTOL) capabilities. It has complete autonomy in mission execution and allows for the integration of diverse payloads.
With the ability to execute missions at altitudes of up to 15,000 feet, the BAHA has a maximum flight duration of six hours with a gas engine and covers a range of up to 80 kilometers. It also features a 5-kilogram payload capacity and a 3.7-meter wingspan. The system, designed for quick deployment by two individuals and operation by a single person, can be mission-ready within minutes, according to HAVELSAN.
Tested in various regions, challenging climates, and operational conditions, the system has been improved based on feedback from security forces.
HAVELSAN has achieved export success with the BAHA in Africa and Central Asia this year. After successful tests, it is now available for domestic use by security forces.
Turkish Aerospace Industries (TAI) will begin distributing Anka, its medium-altitude long-endurance class UAVs, to several countries this year, reported the Daily Sabah. Chief Product Engineer, Ziya Dogan, added that an export deal was signed with another country for the delivery in 2024, but did not mention anything specific.
The Anka UAV has more than 30 hours of endurance and a payload capacity of more than 350 kg. It is designed primarily for the Turkish Air Force.
Anka performs day and night all-weather reconnaissance, target detection and identification and intelligence missions. The UAV also features autonomous flight capability, including automatic takeoff and landing.
The Mw 7.8 and Mw 7.5 Kahramanmaraş Earthquake Sequence struck near Nurdağı, Türkiye, on Feb. 6. It collapsed several buildings and has claimed more than 50,000 lives. The impact of the initial earthquakes was very severe, but to make matters worse, later in February, a Mw 6.4 tremor struck near Antakya, a city near Türkiye’s border with Syria. This created further damage to infrastructure and claimed more victims.
Image: Screenshot of video from NBC News
The Specifics
The United States Geological Survey reports that the earthquake resulted from strike-slip faulting at shallow depths. The earthquake sequence displaced numerous fault segments within the East Anatolian Fault zone. Early estimates indicate about 185 miles of fault length ruptured. Parts of the North Anatolian Fault shifted 10 feet, while segments of the East Anatolian Fault slid more than 30 feet.
Historic Site Suffers
Gaziantep Castle dates back to the second millennium B.C. It has been used in many capacities throughout history, and more recently, stood as a museum for visitors to learn about its rich history. The castle was reduced to rubble in the earthquake. Other historical sites that sustained damage include the Yeni Mosque and the ancient city of Aleppo in Syria.
Image: Screenshot of CNN video
Earth Opens Up
The earthquake destroyed cities all over Türkiye and northern Syria, but they are not the only areas that suffered dramatic effects. A verdant olive grove in Tepehan, Hatay Province, Türkiye, was completely divided when the ground split, creating a 984-foot-long valley in the middle of the grove. The valley is more than 130 feet deep and has created issues for the 7,000 people that inhabit the area.
On Feb. 6, a magnitude 7.8 earthquake struck Turkiye and northern Syria creating enormous damage throughout both countries. (Image: mustafaoncul/iStock /Getty Images Plus/Getty Images)
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.
Figure 1. Phase shift in InSAR observations due to ground movement. (Image: Simon Ndiritu)
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).
Figure 2. A simplified diagram of an SDR-based SAR system is shown, which employs a mobile-transmitter fixed-receiver passive bistatic SAR (MF-PB-SAR) architecture. (Image: Simon Ndiritu)
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.
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.
GMV is using high-resolution optical imagery as a part of emergency management efforts, to map the population and infrastructure of several cities in Turkiye after the 7.8 magnitude earthquake. The imagery of the aftermath is thanks to Europe’s Copernicus program, which keeps satellites and Earth observation services operational to support management and decision-making in different areas, particularly in the field of emergency management.
The satellite images show the challenge faced by rescue teams and reveal the massive amounts of destruction caused in cities across Turkiye and northern Syria. (Image: GMV)
GMV is one of the suppliers of Copernicus program infrastructure. GMV monitors the database architecture and ensures its integrity, analyzes the data required by the service chains, and identifies the most suitable technologies to keep the entire program operational.
GMV is working with the EU Civil Protection Mechanism’s Emergency Response Coordination Center to keep them updated on the ongoing emergency situation.
For more on the emergency satellite mapping, visit the Copernicus website.
Three earthquakes of magnitude 6 or larger have occurred in Turkiye and northern Syria since 1970. The largest was a magnitude 6.7 earthquake in January 2020. (Credit: USGS)
On Feb. 6, a magnitude 7.8 earthquake struck Turkiye and northern Syria collapsing buildings and killing more than 2,000 people, followed by magnitude 6.7 aftershocks. The impact of the earthquakes was significant and ranks in the red for economic losses and orange for fatalities, according to the United States Geological Survey (USGS).
The USGS reports the earthquake resulted from strike-slip faulting at shallow depths. It appears to be associated with either the East Anatolia fault zone or the Dead Sea transform fault zone.
Historical buildings throughout Turkey have been severely damaged, including the Yeni Mosque and the Gaziantep Castle, which date back thousands of years.
War-torn Syria — specifically Aleppo, Hama and Latakia — have also sustained severe damage to infrastructure that was already fragile.
The effects of this earthquake were felt as far as Lebanon and Israel.
Parts of the historic Gaziantep Castle collapsed, as it lies close to epicenter of the magnitude 7.8 earthquake. (Image: JudyDillon/ iStock / Getty Images Plus/Getty Images)
Historical Gaziantep Castle’s east, south and southeast bastions collapse, leaving debris scattered on the road after major 7.4-magnitude earthquake struck Türkiye’s southeasthttps://t.co/5j2soYI6hCpic.twitter.com/1n6whCr2gY
