This app is intended to try to show how both models work. Flat and ball Earth. You can see how altitudes relative to horizon appear to be and see distances between points. The results are not perfect so don't use any of the results here as confirmation for anything. Even though both models received accurate sizes and good quality images as resource, both models appear to have problems and both do not represent reality. For instance ball model, the distance to the moon is correct but the moon itself looks to small, similar to earth being seen from the moon. As for flat model there is no way to know if any of the distances between cities/locations are correct and depending on the image used, results may slightly vary. Still it should be good for keeping the debate alive I guess.