New software to create 3D maps of buildings in minutes

Scientists have developed a new software that can create 3D models of entire buildings within minutes, an advance that may help survey entire districts.
The new method works by purely optical means. It is based on comparing multiple images, which are taken on a tablet by a camera with a fisheye lens.
The software analyses two images of a building's facade taken from different positions. For each piece of image information, each pixel in an image, it searches for the corresponding element in the other, researchers said.
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.

Earlier models were restricted to the outlines of buildings and basic features such as window openings and doorways.
The new software shows architectural details such as the arrangement of bricks in a stone facade.

It offers some key advantages over existing methods. One advantage is that it can be used in sunlight, researchers said.
"Other systems work using a measuring grid of infra-red light," said Torsten Sattler from ETH Zurich in Switzerland.
An infra-red camera captures the projected image of the grid and uses this to generate a three-dimensional map of the object, researchers said.
"This technique works well indoors," said Sattler, adding that the method has clear advantages outside as well.

The project allows even whole buildings to be mapped for the first time, due to the fisheye lens and the device's high processing power, researchers said.
"In future, this could probably even be used to survey entire districts," said Sattler.
Real-time feedback is possible because, due to its high processing power, all of the calculations are performed directly on the tablet. This also paves the way for applications in augmented reality, researchers said.
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.