Month: October 2016
The new three-dimensional map of Earth has been completed. Mountain peaks and valley floors across the globe can now be seen with an accuracy of just one metre. The global elevation model was created as part of the TanDEM-X satellite mission; it offers unprecedented accuracy compared with other global datasets and is based on a uniform database. The approximately 150 million square kilometres of land surface were scanned from space by radar sensors. “TanDEM-X has opened up a whole new chapter in the field of remote sensing. The use of radar technology based on two satellites orbiting in close formation is still unique and was key to the high-precision remapping of Earth. In this way, DLR has demonstrated its pioneering role and satisfied the prerequisites for the next major development step in satellite-based Earth observation – the Tandem-L radar mission,” says Pascale Ehrenfreund, Chair of the Executive Board of the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR).
(The first TanDEM-X mosaic of Iceland. Credit: DLR)
The quality of the global elevation model has surpassed all expectations. Exceeding the required 10-metre accuracy, the topographic map has an elevation accuracy of a single metre. This is a result of excellent system calibration. The distance between the two satellites in formation flight, for example, is determined with millimetre precision. The global coverage achieved by TanDEM-X is also unparalleled – all land surfaces were scanned multiple times and the data was then processed to create elevation models. In this process, DLR’s remote sensing specialists created a digital world map consisting of more than 450,000 individual models with pixel by pixel height detail – creating a special kind of three-dimensional mosaic.
TerraSAR-X and TanDEM-X have long exceeded their specified service lives and continue operating faultlessly and in such an efficient way that they still have enough propellant for several more years. Completion of the 3D world map does not signify the end of the mission. Due to the special nature of the formation flight, further scientific experiments are scheduled. Moreira points out: “Earth as a system is highly dynamic, which is also reflected in its topography. Through frequent updates, we could capture such dynamic processes systematically in the future. This is the primary goal of the Tandem-L mission that we have proposed.” (Image Comparing the Shuttle Radar Topography Mission (SRTM) elevation model from 2000 and the data acquired by TanDEM-X over the opencast lignite mine at Hambach, near the German town of Jülich, the improved accuracy is impressively demonstrated. In addition, the changes over the past 10 years can be seen – the mining activity has progressed considerably.)
New Synthetic Aperture Radar (SAR) methods will enable diverse data for exploration of the global ecosystem to be provided within short periods of time. The Tandem-L successor mission could provide a current elevation image of Earth’s entire landmass every eight days and thereby capture dynamic processes in a timely manner. This would also make it possible to contribute to the review of international climate and environmental agreements. New radar methods and innovative missions such as Tandem-L are set to contribute to gaining a better understanding of dynamic processes in order to protect and preserve Earth Completion of the TanDEM-X global elevation model has now paved the way for the next dimension of radar remote sensing.
About the mission
TanDEM-X is being implemented on behalf of DLR using funds from the Federal Ministry for Economic Affairs and Energy (Bundesministerium für Wirtschaft und Energie). It is a Public Private Partnership (PPP) project operated in conjunction with Airbus Defence and Space. DLR is responsible for providing TanDEM-X data to the scientific community, mission planning and implementation, radar operation and calibration, control of the two satellites, and generation of the digital elevation model. To this end, DLR has developed the necessary ground-based facilities. The DLR Microwaves and Radar Institute, the DLR Earth Observation Center and the DLR Space Operations Facility in Oberpfaffenhofen are participating in the development and operation of the ground segment of TerraSAR-X and TanDEM-X. Scientific coordination is the responsibility of the DLR Microwaves and Radar Institute. Airbus Defence and Space built the satellites and is sharing the development and operating costs. The company is also responsible for the commercial marketing of the TanDEM-X data.
Every year Bihar is deluged by floods that submerge roads, destroy homes and wash away crops, leaving the disaster management authority struggling to monitor and assess the damage, and to distribute aid effectively. But new satellite mapping of flood-prone areas should transform disaster response by equipping authorities with near real-time information about inundated villages, officials said.
Bihar, which borders the Himalayan nation of Nepal, is India’s most flood-prone state. More than 70 percent of its total geographical area is at risk of annual floods, which put lives at risk and lead to heavy financial losses.
A major challenge for the Bihar state disaster management authority (BSDMA) has been mapping and monitoring flood-hit areas, according to the International Centre for Integrated Mountain Development (ICIMOD), which works to promote development across the Hindu Kush Himalayas.
(Flood-affected villagers use temporary rafts as they navigate through the floodwaters of river Ganges and move to safer grounds, after heavy rains at Patna district in Bihar August 29, 2013. Credit: REUTERS)
Since floods started in the state last month, more than 200 people have died and more than 300,000 have been forced from their homes, disaster officials said. ICOMOD has helped generate innovative flood mapping for 33 districts in Bihar and an online flood information system that is allowing faster response to a crisis, quicker damage assessment, and better risk management than with conventional methods, said officials from ICIMOD, based in Kathmandu.
“Traditionally, field teams are organised and dispatched to flooded areas to map floods. This can be time-consuming and operationally difficult during a flooding event,” Shahriar M. Wahid, a senior ICIMOD hydrologist, told the Thomson Reuters Foundation via email.
While “satellite-sourced flood maps alone cannot provide early warning to (the) at-risk population”, he said, satellite data, in combination with flood simulations, can do this. If flash floods triggered by torrential rain occur in Nepal, Bihar’s residents can expect to see inundations about eight hours later, according to data from the BSDMA. Wahid said the new flood maps will be most useful for the distribution of relief, assessment of damages and to determine crop insurance payouts, among other benefits.
The project uses satellite technology that penetrates cloud cover, unlike optics-based satellite imagery. This is useful in the Himalayan region where monsoons bring thick clouds. Flood maps can be generated within five to six hours after raw satellite data is received. The floods are circulated to government officials and relief agencies through a satellite communication network. Space satellite technology is often touted by disaster relief experts as an important tool in managing the growing number of climate-linked disasters around the world. But the cost of such technology for developing countries, even fast-growing ones like India, can be a challenge.
Satellite maps can also aid prevention because they act as a template for years to come, recording rainfall patterns and data from the water department, among other factors, ICIMOD said.