Yun Zhang and his team of researches used two satellite images. Each image was 16 kilometres by 16 kilometres. One of them was a black and white high definition image and the other one was a colour low resolution picture. They then used small angle difference to find moving objects. Thus the team developed algorithms that could detect moving objects and calculate speed trajectory and direction. The algorithms used the average speed to build maps of speeding hot-spots, and areas of congestion. Researchers believe that this data can be used by road builders to streamline traffic flow, or by police to focus speed traps.