Earth Change Monitors
Historical Animated Pole Plots
The series of dates below allow the selection of animated graphical plots of Earth's north polar axis motion historically. The dates span the years 1846 to 2009 in three different resolutions. The polar positions for the earliest dates were calculated approximately every 37 days for a total of ten per year. From 1890 to 1973 the poles position was calculated approximately every 17-18 days, or a total of 20 positions per year. From 1973 on the poles position was computed daily with much higher precision than previous years.
The animations of Chandler's Wobble before 1973 are shown as open circles and ellipses. Each ellipse represents a single plotted position of the North Pole's position. The calculated position is in the middle of the ellipse, and the size of the ellipse is directly proportional to size of the IERS's published error values.
Animations after 1973 are not displayed with error values because the errors are so small as to be below the resolution of the display.