A computer-readable map format and methods of constructing the map format are disclosed. The map format includes location information for a plurality of background objects. At least one of the background objects is a seasonal background object and the location information associated with the seasonal background object is identified during a season in which an obscuration level associated with the seasonal background object is at a minimum. The obscuration level can be based on the amount that the seasonal background object is obscured or based on the amount of obscuration caused by the seasonal background object.