The input data is optical imagery which is gathered, reviewed and delivered state by state. Imagery is made available within a year of acquisition. It is updated every other year for each state so half the US states are completed one year, and the other half the following year. Before 2018, it has a 1m resolution, and since then it has 0.6m resolution or ground sample distance. There is an accuracy within 6 meters at a 95% confidence level when inspected locations are matched to photo-identifiable ground control points.