The ETH scientists' method works by comparing multiple images, which are taken by the tablet’s camera with a fisheye lens, and uses the principle of triangulation in a manner similar to that applied in geodetic surveying. The software analyses two images of a building's façade that were taken from different positions. For each pixel in one image, the software searches for the corresponding element in the other. From these two points and from the camera's known position and viewing angle, the software can determine how far each picture element is from the device and can use this information to generate a 3D model of the object.
One advantage of this software is that it can be used in sunlight rather than existing methods which use infra-red light to project a grid onto an object and uses this to generate a 3D map of the object. As sunlight also contains infra-red components it can interfere with the measurements.
As the researchers have found, the mapping of large objects is plagued by calculation errors in respect of the 3D coordinates. "It isn't that easy to differentiate between correct and incorrect information," explained Torsten Sattler, a postdoc in the ETH group. "We solved the problem by programming the software to scrupulously delete all dubious values." Thanks to a preview mode the user always knows for which building areas they have collected enough information and which still require scanning.
This real-time feedback is possible because, thanks to its high processing power, all of the calculations are performed directly on the tablet. The scientists say that this could pave the way for applications in augmented reality. One example is a city tour in which a tourist carries a tablet as they move around a city in real life. If they view a building 'through' their tablet, additional information about the building can be displayed instantly on the screen. Other potential applications include the modelling of buildings, the 3D mapping of archaeological excavations, and virtual-reality computer games.
Furthermore, the technology could be integrated into cars to allow them to automatically detect the edge of the road, for example, or the dimensions of a parking space. Accordingly, the current project has also utilised findings from the EU's V-Charge project for the development of self-parking cars.
"Our software is now part of Google's software database. Of course, we hope that Google will make our technology available to end users and include it as standard in the next version of the Tango tablet," said Sattler. "Our dream is that someday every mobile device will include this function, allowing the development of apps that utilise it."
At CES 2016 in Las Vegas, Lenovo announced its intention to put a smartphone with the Google Tango technology platform on the market in summer 2016. Although there were no pictures of the device, which also doesn’t have a name, as it is still in development
