We know that the shortest distance is straight line between two points. but it's often not simple when hams communicate with each other from around the world. Because it's not the shortest distance geographically if we connect two points directly on world map, we need to select the right direction of antenna to achieve the better communication effect. Especially for directional antennas, such as Yagi antennas. we must rely on the great circle Maps.
The Great Circle Maps we usually use for amateur radio, also be called "equal distance direction circle map". It is a spherical expansion map with a certain position on the earth as the center point, which can intuitively indicate any direction and distance between any position to the center position on the earth. so it's the important materials in amateur radio communication activities, and also very practical science maps.
If you need the Great Circle Map, please search for Great Circle Maps on Google to download the free software developed by SM3GSJ. then you can generation your own Great Circle Map.