Navigation system and method of determining a vehicle position A navigation system comprises an image sensor configured to capture image data. A map database comprises street lighting data which includes, for a plurality of street lights (41), position data indicating a position (31) at which a street light (41) is installed and height data indicating a height (34) at which a light source (42) of the street light (41) is located. A processing device is configured to refine a position estimate by analyzing the image data using the street lighting data.