Methods and systems for generating and using localization reference data

A system for determining a position of a vehicle relative to a digital map, the digital map comprising data representative of navigable elements of a navigable network along which the vehicle is travelling, the system comprising processing circuitry configured to:

• obtain localisation reference data associated with the digital map for a deemed current position of the vehicle along a navigable element of the navigable network, wherein the location reference data comprises at least one depth map indicative of an environment around the vehicle projected on to a reference plane, the reference plane being defined by a reference line associated with the navigable element, each pixel of the at least one depth map being associated with a position in the reference plane associated with the navigable element along which the vehicle is travelling, and the pixel including a depth channel representing the distance to a surface of an object in the environment along a predetermined direction from the associated position of the pixel in the reference plane;
• determine real time scan data by scanning the environment around the vehicle using at least one sensor, wherein the real time scan data comprises at least one depth map indicative of an environment around the vehicle, each pixel of the at least one depth map being associated with a position in the reference plane associated with the navigable element, and the pixel including a depth channel representing the distance to a surface of an object in the environment along the predetermined direction from the associated position of the pixel in the reference plane as determined using the at least one sensor;
• determine a longitudinal alignment offset between the depth maps of the localisation reference data and the real time scan data by calculating a correlation between the localisation reference data and the real time scan data;
• determine a lateral alignment offset between the depth maps, wherein the lateral offset is based on a most common lateral offset between corresponding pixels of the depth maps;
• and
• use the determined longitudinal and lateral alignment offsets to adjust the deemed current position to determine the position of the vehicle relative to the digital map.