By Isabelle Robinson, M.Sc.Dec 21 2018.jpg)
Shutterstock.com/sdecoret
The Earth was formed over 4.5 billion years ago and has a surface area of approximately 510.1 million km2. For hundreds of years, humans have tried to accurately map the face of the Earth but these maps can be distorted, outdated or simply just inaccurate.
The problem is that the Earths surface changes constantly and therefore new technology must be employed to keep topological surveys accurate. It is known that earthquakes, volcanic eruptions or floods can rapidly change the surface of the Earth. In contrast, the continents slowly travel across the globe at 8 cm per year, mountain ranges form and coasts erode over long periods of time.
The importance of accurately mapping the Earths surface can help scientists with other areas of research. It is also vital for large infrastructure projects.
Mapping Land Mass
The German space agency (DLR) unveiled their 3D map of the Earth’s land surface in October 2018. The map, which is free for public viewing, used images from two radar satellites to distinguish various heights across the Earths surface.
The two satellites are known as TerraSAR-X and TanDEM-X which use microwave pulses to measure the height of the ground. The two satellites operate in an interferometric mode and often fly side by side. The pair of satellites has been orbiting together for nearly a decade with TerraSAR-X first launched in 2007, flowed by TanDEM-X which was launched in 2010.
While the resolution of the released model is 90 m, the map is an important piece of information as it contains no gaps and has a vertical accuracy of 1 m.
The resolution of the newly released digital elevation model (DEM) is 90 m, meaning the land surface has been divided up into squares that are 90 m along the side. It should be noted that DLR also has similar maps with a rendering of 30 m and 12 m, but these are commercially restricted.
While the map is considered revolutionary, there are still some problems that the space agency needs to address before it can be considered complete. One of these problems is that, because of the type of wavelength used, some of the heavily forested areas are not accurately represented. DLR have plans to remedy this by utilizing a longer wavelength.
"In forests, for example, in the X-band [original wavelength] you get, more or less, the top of the canopy," stated Dr Manfred Zink from DLR's Microwaves and Radar Institute.
"You don't penetrate and see under the leaves. But with the L-band [longer wavelength] we will penetrate; we will see the solid ground. That would enable us to see the vegetation volume in real 3D. It's tomography," he explained.
Mapping Underwater Surface
70% of the Earths surface is underwater. This means that the majority of the Earths surface is hidden from view and orbiting satellites cannot accurately measure the topography under the waves. Measuring the ocean floor is difficult and because of this only 15% of the seabed has been measured in any meaningful or accurate way.
Therefore, the Shell Ocean Discovery XPRIZE was launched. Eight multidisciplinary teams from around the world compete to develop the best robots that can accurately map an area of 500m2 to a depth of 4000m in under 24 hours.
The competition promises $5 million for the winning team and $1 million to those in second place. The favorite team to win Is GEBCO-NF, (General Bathymetric Chart of the Oceans) who uses an AUV from the Norwegian Kongsberg Maritime company. The sea-mapping robotic is deployed using the SEA-KIT. The SEA-KIT is a type of unscrewed surface vessel made from aluminum and propelled using a hybrid diesel-electric system.
There has been a shift in attitude towards underwater mapping in recent time. The ocean industry has decided that it wants to map the entire ocean floor by 2030. Projects like XPRIZE will be extremely valuable to attaining this goal.
"It can be done; it's possible, although it might cost the same as a Mars mission," Rochelle Wigley, GEBCO-NF project coordinator, stated. "That funding is not immediately available. Ocean science hasn't been seen as sexy. That's changing and I think projects like XRPIZE and 2030 are raising awareness, and that's got to be good."
Works Cited
Amos, J. (2018, October 10). German Satellites Sense Earth's Lumps and Bumps. Retrieved from bbc.co.uk: https://www.bbc.co.uk/news/science-environment-45815399
Amos, J. (2018, September 13). Robots Ahoy! Mapping Earth's Surface. Retrieved from bbc.co.uk: https://www.bbc.co.uk/news/science-environment-45503144
Schmidt Ocean Institute. (2018, July 2). Fleet of Aerial, Surface and Underwater Robots Maps Ocean Front. Retrieved from phys.org: https://phys.org/news/2018-07-fleet-aerial-surface-underwater-robots.html
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