There are many image sources used because NorCal covers such a large area. While the most current imagery is desired, because of image quality or availability, older imagery may have to be used. We try to choose from the best available imagery, rather than using a newer image that has overexposed, blown out areas, or long shadows, haze, clouds, or other artifacts that affect image quality. Like any map or aerial photo, they are all outdated as soon as they are created.