The Spanish SIGPAC (Agricultural Plots Information System) is a database, or official register, for which FEGA (ministry of agriculture) and the departments of agriculture of the autonomous regions publish crop fields.
Currently, the data is collected in different formats from each of the sources, and converted into fiboa data sets.
See https://www.fega.gob.es/en/pepac-2023-2027/sistemas-gestion-y-control/sigpac or http://www.mapama.gob.es/es/agricultura/temas/sistema-de-informacion-geografica-de-parcelas-agricolas-sigpac-/ for more information.