Variation, developed by Navigational Algorithms, is a free Android app that helps users with navigation using magnetic compasses. The app uses the World Magnetic Model (WMM2015) to calculate the angle between magnetic and geographic meridians, known as magnetic variation or declination. It helps to indicate the direction of magnetic north from true north, which is useful for navigation purposes.

With Variation, users can add a mark with the variation at their current position for the day by a long click on the map. The app also allows for zooming in and out with the zoom buttons, and has normal and satellite map types. Additionally, users can save their last position automatically and access their GPS location.

The Course Calculator in the app enables users to calculate the deviation coefficients (A, B, C, D, and E) with the Magnetic Compass Windows application, available on the Navigational Algorithms website. Users can enter these coefficients and save them, and the Course Calculator will be able to compute the deviation.

Overall, Variation is a reliable navigation app that provides accurate information and helpful features for users.