Chameleon schreef op 14 april 2016 20:38:
www.economist.com/news/science-and-te...heel interessant!
Even more important for an autonomous vehicle is the ability to locate itself precisely; an error of a couple of metres could place a car on the wrong side of the road. Commercial GPS systems are accurate only to around 5 metres, but can be wrong by 50 metres in urban canyons and fail completely in tunnels. HD maps, however, can include a so-called localisation layer that works with a variety of sensors to position a car within centimetres.
HERE is experimenting with several such layers. One involves extracting features like bridges, road signs and guard rails from images shot by the mapping vehicle, and then comparing them to what the car sees through its own cameras.
TomTom, a mapping firm based in the Netherlands, rejected this process as too unreliable. “We found that trying to model reality down to every single bridge pillar and then triangulating it is too sensitive to change,” says Pieter Gillegot-Vergauwen, one of the firm’s vice-presidents. Problems can arise if, for instance, a tree is cut down or a street scene alters from summer to winter. “There are too many visual changes,” he adds.
Instead, TomTom captures a “depth map” using its mapping vehicles’ LIDARS. This system continuously records the distinctive shapes and distances of roadside scenery, without trying to identify what the individual things are. By considering the whole stretch of road it is possible to correlate the output from the autonomous car’s own LIDAR unit with the pattern of the depth map and calculate its location even if, say, a tree grows or a lorry is in the way, says Mr Gillegot-Vergauwen.