Allow me to explain how the lines of Longitude start generating such errors in the flat earth model.

First, look at the FAQ, the flat earth model is a disk 24,900 miles in diameter, with an equator at half that distance. The equator, then, forms a circle 12450 miles in diameter, with a circumference of 39,112 miles.

Comparing this with the round earth, you see the first discrepancy. The circumference of the equator is off. The round earth is only 25,000 miles in circumference. Why not make the flat earth model have the same equatorial diameter? The fact is, The height of society in Samuel Rowbotham's day lived in Europe and the United States, so the model is most accurate there.

We continue with the flat earth model.

Lines of longitude extend from the north pole to the Ice Wall, there are 360 degrees of longitude equally spaced around the disk. So, at the north pole they all bunch up, and at the Ice Wall, they are as far apart as possible. In fact, each degree of longitude at the Ice Wall is 217.3 miles apart (78225 (diameter of the ice wall) / 360). And at the equator they're only 109.6 miles apart.At any point on the disk, the distance can be calculated between degrees of longitude through simple math.

The cities of Adelaide, Australia and Sydney, Australia are 12.5 degrees of longitude apart, and are at a latitude of 34.5 degrees south of the equator. Do the math, the distance netween them should be 1878 miles. But maps of Australia don't agree with that by a HUGE margin, they place the cities at 740 miles apart.

People in Australia use those maps every day. They would notice such a discrepancy.