Minute Physics explains, once again, how to determine if something is a fact or fiction. In this case there are 10 reasons as to why Earth is round and yes, there are still people who have flat minds.
I like most particularly the experiment with the sticks inserted in the ground and then you measure the radius of the planet by putting those sticks on the same line North- South and then measure the shadow left by each one on the ground.
From that point on you need to plot the formula Θ=tan^(-1)*L1+tan^(-1)*L2 (L1 and L2 being the shadow length) and then you get the angle between the sticks. Knowing the distance between those two sticks you can get the radius: Radius = d/Θ.
At the run of the year I wish you all the best year ever. 😀