Flat-Earth-distance is a Chrome add-on developed by Michael Osincev. It is a free program that allows users to convert distances on the Yandex map to distances on a Flat Earth. With this add-on, users can easily calculate the distance between two points on the map using the ruler tool.

The program uses a simple explanation of the calculations involved. It considers A, B, and C as the sides of a right triangle. A represents the distance from the North Pole to the selected point, B represents the distance from the point to the Prime Meridian at a 90° angle, and C represents the distance from the intersection of B and the Prime Meridian back to the North Pole. The X and Y coordinates on the virtual "world map" are used to calculate the positions of the points relative to the North Pole. By subtracting the X and Y coordinates of the two points, the program determines the distance between them.

Flat-Earth-distance is a useful tool for those interested in exploring alternative perspectives and calculations based on a Flat Earth model. It provides a straightforward way to convert distances on the Yandex map to distances on a Flat Earth, allowing users to gain a new understanding of spatial relationships.