Applications Abound in Defense, Maritime and Engineering
Change Detection Image at Port in Rotterdam, The Netherlands - False color SAR image with 1-m resolution (Spotlight-2 mode) was obtained by combining three observations carried out by different satellites of the COSMO-SkyMed constellation, with red: COSMO 2 on 29/06/2011; green: COSMO 3 on 30/06/2011; blue: COSMO 1 on 07/07/2011. All unchanged features are in black-grey-white color according to their brightness. Colorful features show changes along the time span (9 days) of the observation with ships and boats changing their positions. Faint color variations reveal changes of the content in the fuel tanks in the lower part of the image. Image courtesy of e-Geos.
MDA’s services for the mining industry identify unstable areas for repositioning of equipment or infrastructure to minimize potential damage and avoid injury. It is also used as a validation mechanism before costly real-time monitoring systems are implemented. This image shows wall integrity, courtesy of MDA Geospatial Services, Inc., 2010.
New RADARSAT-2 imaging modes with wider swaths enable broad-area DEMs to be created using fewer images, reducing the time and cost of production. Courtesy of MDA Geospatial Services, Inc., 2010.
Icebergs breaking away from the Antarctic Peninsula on four different dates. Courtesy of MDA Geospatial Services, Inc., 2010.
Gawar, Saudi Arabia Center Pivot Cultivation - The multi-temporal image (in false colors) shows center pivot cultivation in the Arabian desert. The three Stripmap mode images (3-m spatial resolution) were collected by different COSMO-SkyMed satellites over one week. Circular cultivated areas show bright colors indicating changes occurring in both terrain and vegetation due to agricultural activity (irrigation, plant growth, ploughing . . . ). Image courtesy of e-GEOS.
Disturbed Terrain Around Qom Plant, Iran - COSMO-SkyMed 1-meter resolution image (Spotlight-2 mode) over the nuclear facility of Qom in Iranian desert. The black and white background image highlights bright industrial structures and buildings. Dark linear features represent dirt roads and track network around the plant. When the acquisition is repeated after a short time, the coherence of the phase signals between the two images provides additional information about the scene. Red tracks are derived from coherence calculated over a time span of eight days. They show where the stable desert terrain was “disturbed” by the passage of vehicles (both on and off-road) and even animals (randomly distributed tracks on the upper right). This image also appears on the front cover, and is courtesy of e-GEOS.
TanDEM-X Digital Elevation Model of Volcano Tunupa and the edges of the salt lake Salar de Uyuni in Bolivia. The blue and dark blue colors mark the salt pan as the area with the lowest elevation level. Courtesy of DLR
TerraSAR-X-based Surface Movement Monitoring of oil production-related surface displacement phenomena in Burghan oilfield in Kuwait, demonstrating significant subsidence of approximately 10mm/year in the main production center visualized by the orange color scale in the graphic. 16 TerraSAR-X StripMap scenes at 3-m ground resolution were selected from an available data stack over the target area covering a time period between January 2008 and February 2011. These datasets were processed using the Small Baseline Subset (SBAS) radar-interferometric approach. Courtesy of Astrium Services / Infoterra GmbH.
Subset of a Color SAR image (colorized radar image) of Fairbanks, Alaska, U.S. in comparison to the base TerraSAR-X SpotLight acquisition (1.6-m resolution). Courtesy of Astrium Services/Infoterra GmbH.
Whether used to view Earth’s surface through clouds or at night, to measure the thickness of polar ice sheets, to map long-abandoned mines, or to monitor subsidence, synthetic aperture radar (SAR) imaging has become a standard remote sensing tool. While optical satellites have higher resolution, radar imagery is better for change detection. Governments and private companies can use SAR satellites to monitor wide swaths of land or water from relatively low orbits, then follow up with higher resolution systems to zoom in on, say, an unidentified ship approaching a shore. Capacity continues to grow, as new satellites are launched. The two biggest challenges now for this segment of the geospatial industry are to develop software tuned to the requirements of specific users and to train them in using the data.
Editor’s Note: The Korea Aerospace Research Institute and Fugro declined to be interviewed for this article.
Status and Trends
Radar is a growing market. “From a mostly defense and maritime business,” says Andreas Kern, Director of Business Development and Sales for the European company Astrium GEO-Information Services, which owns TerraSAR-X, “it has grown 20-25 percent per year over the last three years, and the variety of user requests keeps expanding.”
John Hornsby, VP of Geospatial Strategy of the Geospatial Services Division at the Canadian firm MacDonald Dettwiler and Associates Ltd. (MDA) — the commercial provider of RADARSAT-1 data and operator of RADARSAT-2, a SAR imaging satellite that was financed primarily by the Canadian government — has seen his company’s business increase significantly in the past 18 months. For example, he says, Canadian government agencies have dramatically increased utilization for maritime monitoring and surveillance making it a core tool for fulfilling their operational mandates.
“With regards to change detection,” Hornsby says, “clients need the tools to better utilize radar data, and we are developing them. It has been a challenge to develop exploitation systems, because they have to be very tuned to the requirements of specific users. For example, agricultural users need to fully utilize the polarmetric capability of the imagery, which is complex to do – to identify particular crop types. Defense users, on the other hand, are looking more at changes over time and require different techniques to fully exploit the imagery.”
One indicator of the growing recognition and acceptance of radar imaging is that the National Geospatial-Intelligence Agency (NGA) has put in place contracts with major SAR providers, as it had previously done with optical data providers, so as to have a mech- anism to routinely access SAR data. This is one reason Hornsby expects to see an increase in utilization. “We are collaborating with our Italian and German colleagues to build the utilization market,” he says. No commercial U.S. radar system exists currently.
Jack Hild, Vice President for U.S. Defense Strategy at DigitalGlobe, spent 30 years at the NGA, where he was continually in charge of operations in which analysts used radar. While acknowledging that commercial radar technology is very good, he says that he would be surprised to hear that someone had come up with a striking new use for radar imaging recently. “I visited all the major providers within the past few months and did not see anything new,” he says. While radar is “a great supplement” to electro-optical (EO) Earth observation, he points out, it will not replace it. “Radar and EO will continue to grow globally, but I don’t see double-digit growth. I do see evolutionary growth, as more nations see the value of remote sensing for security and resource management requirements.”
Neither DigitalGlobe nor GeoEye have any radar capabilities on current satellites. “We are looking for a way to establish partnerships with providers of radar data,” says Hild. “Depending on the end use and the customer, we may want to do the analysis ourselves, and sometimes we would rely on our partners for some of the advanced processing.”
Markets and Applications
Sales of radar data are still mostly business-to-government (B2G) and business-to-business (B2B); however, consumer applications are the next most logical area for growth. “The path for consumer applications is going to be longer,” says Kern, “and will require using multi-source data fusion to create derived products and solutions.”
Meanwhile, the range of applications for radar imaging is rapidly expanding. “I’ve seen some great work in using radar to monitor subsidence, in conjunction with autonomous ground sensors,” says Hild. “It’s also been useful for monitoring ice movements in maritime shipping channels and always has a role to play in weather-related natural disast-ers, such as Hurricane Irene.”
Radar is essential to meet imagery requirements in countries in persistently cloudy areas, he points out. “Clouds happen and you can’t always get the picture that you are hoping to get with EO data, but customers more and more have an expectation that they can get imagery at any time. For example, for monitoring ships, they want a guarantee that they will always be able to report whether or not a ship is still docked at port.”
One of the most important applications for radar is maritime surveillance — called maritime domain awareness in the United States — which involves monitoring ship traffic over very large areas. The Canadian Department of National Defence (DND) has recently brought into operation two new stations, on Canada’s east and west coasts, using radar to produce ship detection within minutes.
Hornsby points out, “Building on the strength of the RADARSAT system for maritime monitoring, we are also improving ship detection capability with new operating modes. In this case, new modes have been created which are more effective in identifying vessels. The trade-off is a reduction in appearance of the overall image but for this application, that is not important. The key is getting the ship information.” Real operational users such as DND are embracing the capabilities of satellite radar imaging as performance has improved to meet their specific needs.
The key concept is the transition from application to operational service, argues Luca Pietranera, Head of COSMO Product Innovation and Technical Support for the Italian company e-GEOS S.p.A., the commercial provider of COSMO-SkyMed constellation data. This transition means providing the data in near real-time to a user, such as a coast guard. “We can provide a fully integrated system. Within minutes of when a receiving station receives an image from a satellite, we can process it and integrate it into the information system of the end user. We can do this because we have a fully integrated system, and the frequent revisit provided by our constellation is a key factor for the success of the service.”
Many of these applications are made possible by the use of interferometric SAR (InSAR) and interferometry, the discipline that studies the phase of the SAR signal and its variations. “The phase signal can be regarded as an accurate measurement of the distance between the satellite and the target,” explains Pietranera, who develops new fields of application for radar data, mostly by exploiting change detection. “When you compare two images looking just at the backscatter data, you can see changes in objects that are one meter wide or bigger (i.e. wider than the pixel size). However, if you analyze changes in the phase signal — the first step is coherence analysis — you can see whether a change occurred in objects that are the size of the wavelength (a few centimeters).”
He continued, “Due to the sensitivity of imaging radar to artificial structures and 3D structures with corners, change detection monitoring can be ‘focused’ on those structures, as illustrated by the image of the port in Rotterdam, The Netherlands. The observations can be repeated very frequently in time and, on top of this, radar wavelengths are not affected by changes in observing conditions (such as atmospheric transmission, presence of haze, which can cause ‘spurious effects’ when analyzing change detection in optical imaging).”
“Interferometric processing techniques, especially when coupled with COSMO-SkyMed’s high spatial resolution and frequent revisits,” Pietranera says, “can provide significant information for defense and security applications (by detecting disturbances created by human activity, such as the action of wheels on bare terrain), but also to monitor long term land stability (subsidence, landslides, or earthquakes), or even to provide control on agricultural activities.”
InSAR is particularly useful in the oil and gas industry (to monitor oil fields), in civil construction (to detect potential sinkholes), and in mining (to monitor subsidence). Regarding the latter, in the eastern United States, active mines are being monitored, and forgotten mines are being detected using GPS.
Astrium’s most important vertical markets are defense and the oil and gas industry. In the past year, the company has begun to address the requirements of civil engineers, for example, by using vertical measurements to help operators secure airport safety, and to help large construction projects monitor subsidence. It has also developed methods for collecting from space new ground control points (GCPs), which are needed, for example, to ortho-rectify satellite imagery. “Thanks to the extraordinary accuracy of TerraSAR-X,” says Kern, “we can generate GCPs by collecting on specific points and then triangulating with better than 1-meter XYZ. This is especially cost-effective when it is too expensive or dangerous to put people on the ground. Thus, radar complements terrestrial differential GPS, though it will not replace it.”
Astrium’s data is often used for emergency support, Kern points out. For example, the flood-mapping program it developed with Trimble, which automatically derives flood masks and compares pre- and post-flood data, is used by emergency response authorities, currently especially in Asia and South America, but also for insurance claims.
Another key application of radar data, Pietranera points out, is monitoring the polar regions — especially the North Pole, which is becoming more important strategically, creating a big demand for monitoring. As ice melts, new shipping routes are becoming available. The most famous is the Northwest Passage through Canada’s polar islands. “These routes are very long and very extended in longitude,” he says. “Therefore, it requires a lot of satellite capacity to monitor them and to provide safety information to shipping companies, to national authorities, and to vessels going along the route.”
Helping End Users Interpret Radar Data
Radar is becoming mainstream in several communities, such as intelligence, the military, and agriculture. However, according to Pietranera, the organizations that consume the data have many people who are trained to interpret optical data, which is simpler to do, but not enough people trained to interpret radar data. When it comes to the latter, “advanced processing tasks are almost always handed off to specialists, such as image scientists,” says Hild.
To bring their current and potential customers up to speed, MDA, e-GEOS, and Astrium in May formed a Commercial Synthetic Aperture Radar Satellite Working Group (CSARS WG), under the aegis of the United States Geospatial Intelligence Foundation (USGIF). They are now producing manuals, workshops, and exercises to explain the capabilities and advantages of space-based SAR, as well as to provide hands-on learning and training for users.
“We have recently released an image intelligence manual named TIM — the TerraSAR-X IMINT Manual,” says Kern. “It compares the TerraSAR high resolution radar imagery to WorldView high resolution optical imagery to show and explain to image analysts what they are seeing in the radar images and what the key differences are. It is a new teaching and learning tool.”
One reason that his company’s radar images are more difficult to interpret than those produced by optical satellites, Kern explains, is that they are typically in black and white. To help overcome this problem, Astrium has developed methodologies to provide color radar imagery, not only as multi-temporal imagery but now even with a single data take at full resolution. “As we do not need to use polarizations either, we achieve a top-quality resolution, then we translate speckle into color coding, thereby customizing the radar data to the appearance of the optical image to be overlaid. Color SAR has good potential, especially in cloudy areas. You merge whatever optical data is available — which is always best for thematic mapping — with the radar data, and produce colorized thematic layers.”
Techniques to process radar data — developed by both satellite operators and software companies — are still on the steep slope of the development curve. “We develop many applications for internal company use, as we are a service provider, and offer value-added products and services based on our own developments,” says Kern. “Some of these products are based on off-the-shelf software, such as Gamma or Sarscape, which we adapted to use for our change detection and surface motion monitoring services. Sometimes we work with partners, such as Trimble, with whom we developed the Flood Mapper, and sometimes we also make such tools available to our customers, who use them within their own working environments. Additionally, we also support software and application developers, such as ERDAS, with sample data and joint training activities.”
New Satellite Launches
Astrium recently launched its second satellite, TanDEM-X, which is now flying in formation and collecting global elevation models. The TanDEM-X mission is currently collecting data for a global homogeneous elevation model of an unprecedented quality, accuracy, and coverage, says Kern, who expects the global dataset to be available in 2014.
The company has recently released its updated GEO Elevation Suite, which includes the radar-based Elevation10 product — globally available regional elevation models with up to 5-meter accuracy at 10-meter grid spacing. Astrium also recently began phase A (analysis & assessment) for its follow-on mission, TerraSAR-X2. “We aim to launch it in 2016,” Kern says. “It should bring improved collection capabilities, especially resolution down to 25 centimeters.”
In November 2010, e-GEOS launched the last of four identical satellites, all of which orbit at an altitude of about 620 kilometers. “We now have the full constellation in orbit and COSMO-SkyMed is at its maximum capacity,” says Pietranera. “We can task the satellites separately or use them together to cover large areas faster or to revisit the same locations more frequently. This is very important for many applications, especially those that require analyzing change over time.”
Next year, the European Space Agency (ESA) will launch a new mission, Sentinel 2, which will be a continuation of its previous, highly successful ERS and ENVISAT missions. It will use the C band and will have a resolution in the tens of meters. This will be very good for covering large areas, Pietranera points out, though the imagery will not be as fine-grained as that generated by COSMO-SkyMed, which uses the X band and has a resolution of one meter.
Korea’s Multi-Purpose Satellite-5 (KOMPSAT-5), the country’s first SAR satellite, will operate in low earth orbit (LEO) and carry an X-band SAR. Built and operated by the Korea Aerospace Research Institute (KARI), its primary mission is to provide high-resolution mode SAR images of 1-meter resolution, standard mode SAR images of 3-meter resolution, and wide-swath mode SAR images of 20-meter resolution. During its five-year mission, it will execute all-weather and all-day observations of the Korean peninsula. The launch, repeatedly delayed, is now scheduled for November 2011 (www.satelliteonthenet.co.uk/index.php/launch-schedule).
Radar imaging satellites — which have lower resolution than optical ones, but are better for change detection — have become a standard tool for intelligence, military, agricultural, and other applications and are essential to meet imagery requirements in persistently cloudy regions. Two European companies recently launched radar satellites and new ones are under development in Europe, Korea, Brazil, and China. Brazil and China are considering the development of a new family of radar satellites to monitor deforestation.
Sales of radar data are still mostly to governments and businesses, but consumer applications are the next area for growth. The two biggest challenges now for this segment of the geospatial industry are to develop software tuned to the requirements of specific users — for example, the different change detection requirements of agricultural and military users — and to train them to interpret radar data, which is harder to interpret than optical data.