Declination_Calculator11Declination Calculator (ID: boundingGeographicBoundingBox) The IGRF is a global model that extends back to the begining of the 20th Century and is updated every 5 years to include a forcast model for the following 5 years using observations of the Earth's magnetic field over time to interpolate at E: 180, W: -180, N: 90, S: -90#footprint-180,-90 180,-90 180,90 -180,90 -180,-90