Secular variation of magnetic declination for the past 500 years from Empire to Republic in Anatolia

Seydi Ali Reis first mentioned the declination angle in his book titled Kitab-ı Muhit in 1554. Kitab-ı Cihannüma (1654), Füyuzat-i Mıknatisiye (1731), and Mârifetname (1757) gave the magnetic declination angle values in Anatolia. We have compiled magnetic declination data from 1500 to the present day in Anatolia and Istanbul. The plot of the magnetic declination angle was drawn for the first time using historical data between 1500 and 1947 for Istanbul. Three new magnetic declination maps for the periods of 1909–1910, 1970 and 2009 were produced for Turkey. The annual change map based on the data of 1970 and 2009 is also given for whole Turkey. The agonic line extending in NW-SE direction between Sinop and Antep divides Anatolia into two regions in 1910. The mean declination values obtained from qibla direction measurements made by the Presidency of Religious Affairs in all mosques give 3.11° E for 1970 and 4.74° E for 2009 in Turkey.