Ground control points are necessary for achieving the required accuracy of the orthophotography. Information included in this data include the control points' x & y location, description, and elevation.This is a MD iMAP hosted service layer. Find more information athttps://imap.maryland.gov.Feature Service Layer Link:https://geodata.md.gov/imap/rest/services/Imagery/MD_ImageryAcquisitionFlightInformation/FeatureServer/0