When Audi travelled a self-driving A7 car concept along the 550 miles from San Francisco to Las Vegas last January for the CES trade show, it not only had a vast array of sensors onboard (including laser scanners and 3D video camera) but also a map matching technology invented by TomTom.
Because GPS and other GNSS constellations have their limitations, some years ago TomTom started to research other techniques capable of precisely locating a car on a road. The Dutch company came up with a technology – which they patented – internally called Road DNA.
The basic principle of Road DNA is that it correlates the real-time vision of cameras fitted on a car with a database of 2D pictures from both sides of the road. With that it can precisely position a car on a road at a centimeter level at high speed.
What might seem simple on paper is however quite complex in the reality; it needs to overcome several hurdles. First the image correlation algorithm has to be tolerant to road changes, for example trees with or without leafs depending on the season, snow, etc.
Second, it requires to work with a low processing power and a low latency. Third it needs to be scalable in terms of requested storage size.
“The need for high amounts of data or processing power, are often an obstacle in other positioning proposals found in the automotive Highly Automated Driving developments,“ TomTom explained to GPS Business News.
At that level TomTom worked on making the images as small as possible while maintaining enough patterns to do the map matching. According to Pieter Gillegot-Vergauwen, vice president product management Maps at TomTom, the Road DNA database represents around 25 Kb per km of road. A car could therefore embed this data on on-board cost efficiently or query it on demand through a wireless network.
When it comes to reliability, the company explained it has been testing its image correlation algorithm over the last two years and has risen to 98% correlation between images in the Road DNA database and the reality as seen by car cameras. Obviously this technology will be used in collaboration with GPS and other GNSS (GLONASS, for example) sensors.
Road DNA is still in development and not yet a commercial product and TomTom has not committed yet to a launch date, the company said to GPS Business News.