Mark Skoog, an aerospace engineer at NASA's Armstrong Flight Research Center, led the development of new software that stores terrain data in a more efficient and accurate way. The achievement, Skoog says, opens the prospect of anyone – yes, anyone – being able to fly.
Originally developed to render digital terrain maps, or DTMs, for military airplanes requiring course correction, the repurposed system integrates encoding and decoding algorithms to provide a 5,000:1 compression ratio. A 22-megabyte (22 MB) digital terrain map that previously could be compressed only down to 5.5 MB, for example, can now be shrunk to a tiny 4.4 kilobytes (4.4 KB).
The result: Users can access and create customized the maps from a variety of data sources and interfaces, including tablets and smart phones. The technology, an Electronics category winner in the 2016 ‘Create the Future’ design contest, enables an aircraft-based system to store a greater number of DTMs and provide real-time rendering of local maps. Such capabilities support automated ground collision avoidance.
Tech Briefs: What did you develop?
Mark Skoog: We developed a special encoding process for terrain elevation data: these digital maps that are available from several different sources. We store them in a way that is more appropriate for aviation safety. To do so requires a little bit of manipulation of the data, to bring it into a more appropriate form to support this automated ground collision avoidance capability.
Tech Briefs: Why is a digital terrain map so important in aerospace applications?
Skoog: An aircraft design is very, very sensitive to additional weight and drag. Any time you have to penetrate the outer mold line to add a sensor to the aircraft, it is extremely expensive. Even just having a protruding sensor creates a lot of additional drag, which causes a recurring cost of fuel consumption. If, instead, you could have a digital map, a computer model of the world that is accurate enough to provide the safety, now it becomes nothing more than a software solution.
Tech Briefs: How does the software create these accurate maps?
Skoog: The maps, as they exist today, are what’s called a regular space array of elevation: Terrain elevation values are defined on an even grid spacing of latitude and longitude. You can think of it as even rows and columns of posts, each as tall as the immediate surrounding terrain. Even spacing makes it very easy and quick to access the value at a given geographic location.
If you talk about having an elevation every point on the Earth, that starts to become a pretty sizable file. The size of that database for the entire globe is around 3 gigabytes. Well, aircraft don’t have contemporary storages on them that allow you to carry that much data.
Tech Briefs: So how do you solve that problem?
Skoog: We use a semi-regular array: The posts are not evenly spaced. There is some order to their spacing, but they are not all equal distance from one another. This can take more computer time to access data, but not as much as an irregular array. By using a semi-regular array, we don’t have to repeat the same value over and over where the terrain is flat. This saves tremendously on the file size of the terrain data. We create a series of tiles that are tipped and tilted that represent the Earth, rather than a single post of elevation.
Tech Briefs: What do you mean by tiles?
Skoog: “Posts” assign a singular value for the elevation of a given area. This means some of the terrain in that area is likely higher than that value, and other parts are lower. A single value means that very little data is required to define the elevation of that area.
“Tiles” are a somewhat novel approach that we are using. Instead of posts, think of floor tiles that are tipped and tilted to the average slope of the terrain in that specific area. It takes a couple more numbers to define the terrain elevation, but we can accurately define a much larger area of terrain with a sloped tile than with singular posts.
Additionally, because we have a surface, we can get the elevation at any or multiple locations within a single tile. This is the technique we leverage, a single larger tile representing the terrain elevation of an area as opposed to a number of posts.
Tech Briefs: How does this technology enable the use of digital maps in environments like smartphones and tablets?
Skoog: We reduce file size for the same level of fidelity. On a program like Google Earth, this would mean faster load times to see the detailed three-dimensional terrain. With an electronic flight book app that provides ground proximity warning, it means you can carry much more accurate terrain data over a larger area for an equivalent file size, consuming less storage capacity on your device.
Tech Briefs: What is most exciting to you about this technology?
Skoog: This is a process that makes a ground collision avoid system more efficient and more capable. If you can guarantee or assure safe, autonomous flight, that opens up the prospect for anybody being able to fly. In other words, you don’t have to be a pilot. You don’t have to go through the extensive training that a pilot has to go through. There is also an opportunity for safe package delivery, like companies like Amazon and others are proposing, and even flying cars, which would be very transformative in how we go about our day-to-day lives, especially in the dense urban city environment.
NASA invites you to license the technology. Apply now.
Learn more about the Improved Ground Collision Avoidance System for General Aviation Aircraft and UAVs.
The Software for Aeronautics Collision Avoidancecan be used in aerospace satellites, automobiles, scientific research, marine charting systems, and medical devices.
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