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DLR to develop 3D model of earth using radar data

Berlin, Germany: After a year in service, the German Earth observation radar satellite TanDEM-X, together with its twin satellite, TerraSAR-X, mapped the entire land surface of earth for the first time. The data is being used to create the world’s first single-source, high-precision, 3D digital elevation model of Earth. The German Aerospace Center (Deutsches Zentrum fur Luft- und Raumfahrt; DLR) controls both satellites, generates the elevation model and is responsible for the scientific use of TanDEM-X data.
The satellites imaged earth from different angles and transmitted high-resolution radar data from their orbit at an altitude of 514 kilometres down to the three ground stations – Kiruna (Sweden), Inuvik (Canada) and O’Higgins (Antarctica). “The mission is running better than expected and there have been no unscheduled interruptions in the programmed formation flight of the two satellites. All safety mechanisms are functioning robustly and in a stable manner,” stated Manfred Zink, project manager for the TanDEM-X ground segment at DLR. Over the course of 2011, the distance between the satellites was progressively reduced down to the minimum permitted value of 150 metres.
According to DLR’s press statement, by mid-2013, TanDEM-X and TerraSAR-X will have imaged the complete land surface area of Earth – roughly 150 million square kilometres – several times. The intention is to create an exceptionally accurate, global and homogeneous 3D elevation model that promises to be of equal interest for commercial and scientific purposes.
“The level of precision depends on how well the ground reflects the radar pulses transmitted – and subsequently received – by the satellites,” said Manfred Zink. For example, the Sahara is more difficult to image because the signal literally ‘sinks into the sand’ and is lost. For regions of dense vegetation, such as rain forests, additional imagery and careful adjustment of the distance between the satellites are necessary.
“We are going to be left with a few blank areas on the map, but we do of course seek to minimise these gaps,” added Zink as he thinks about the coming months.
“We want to gain a better understanding of earth as a system and to employ the data for climate and traffic research, for example,” said Irena Hajnsek, scientific coordinator for the TanDEM-X mission. In 2011, she gave the ‘green light’ for 166 of the research applications submitted to DLR. “Most of these originated in the USA and Germany.
The TanDEM-X capabilities are to be used to address questions of land usage and vegetation, hydrology, geology and glaciology,” explained Hajnsek. The two Earth observation satellites can also generate information about the height of the snowline or the change in ice masses of the two polar regions, as well as provide geological maps of regions subject to volcanic and/or earthquake activity. The speed of ships or road vehicles can be measured, as can changes in the natural world.
The work performed by these two radar satellites is also valuable for agriculture. “Based on the height and structure of a plant – such as rapeseed, for example – it is possible to draw conclusions about its quality and biomass,” stressed Hajnsek.
Source: DLR