Map data are overlaid on satellite imagery. A road segment within the map data is identified, and the satellite imagery indicates that the road segment is at a different geographic position than a geographic position indicated by the map data. The endpoints of the road segment in the map data are aligned with the corresponding positions of the endpoints in the satellite imagery. A road template is applied at an endpoint of the road segment in the satellite imagery, and the angle of the road template that matches the angle of the road segment indicated by the satellite imagery is determined by optimizing a cost function. The road template is iteratively shifted along the road segment in the satellite imagery. The geographic position of the road segment within the map data is updated responsive to the positions and angles of the road template.
Now before you get your pitchforks lets look at exactly what Google is proposing here. This is a computer automated process and not one that most GIS people have ever done. Read the claims section to learn more about what exactly this process is. It is interesting that they use TIGER as an example of a dataset that could be improved.
They could simply donate their map updates to OSM. Right my bad, TIGER is a great example of a dataset that doesn’t line up with satellite imagery.