Some chaps went to Worthing Pier and filmed Brighton Pier - and attitude indicators in aircraft have a straight line. Oh and, locally at human being scale, the earth appears flat. I think that was case closed for flat earth.
Yes, locally the earth is flat.
Over one mile the earth is within ±1" of flat:

Not to scale.
Kansas, even allowing for the Globe's curve and the topography is "flatter than a pancake".
More in
Flat Earth Q&A / Re: How can rivers flow on flat earth. « Message by SpJunk on September 16, 2016, 05:50:14 PM »But, to answer the OP, I don't believe that there is any "
one reason that should convince" me that "the earth is flat".
This is because it all "hangs together" and explains the observations of our surroundings that we see with our unaided eyes and with instruments .
That is what I mean when I say that the "Heliocentric Globe Earth works". There are so many little things.
Just one example is that the variation in solar radiation through the day (very relevant to solar panel power) fits the the Globe,
but not the flat earth sun that circles above the earth.
No alternate model I have seen has come close to fitting all observations, though
locally the Babylonian cosmology, flat earth and all, comes close.
But this model cannot be extended to the whole world, other than looking on the earth as only
locally flat.