Some observations

sunrise and sunset DON’T work on a flat earth.

If the earth was flat, then the sun would get smaller during sunset, it doesn’t.
If the earth was flat, the the sun would slow its rate of crossing the sky, it doesn’t.
If the earth was flat, then the sun would appear smaller the further north and south we go, it doesn’t.
If the earth was flat and the sun was small and local, then the sun would appear bigger the higher up someone goes, it doesn’t.
If the earth was flat and the sun was small and local, then the sun would never appear to rise or set due east for the entire globe.

The sun and moon APPEARING to be bigger is an optical illusion.
Actually measuring the angular diameter of the sun and moon shows they don’t change size based on time of day, day of the year, latitude, or elevation.
The sun and moon don’t look larger at the equator than at the poles.
The sun and moon don’t look larger at higher altitudes than at sea level.
The sun and moon don’t look larger at noon than in the morning or evening.
The sun and moon don’t look larger in the summer than in the winter.
These are such basic observations and measurements that if they were true, would have been long established in literature; much like the spherical nature of the earth is long established.

Simple observations and measurements I’ve done which refute the flat earth:

Measure the width of a shadow of a sphere.
Measure the spacing of shadows cast by vertical, parallel pipes.
Measure the precession of a free swinging pendulum.
Highlight the spiral flow of water in a broad, shallow pool that has been allowed to completely settle and still, then drained slowly through a small hole in the center of the bottom.
Measure the size of the sun, moon, and stars at different places, times, dates, and elevations.
Measure the angular rate of the sun, moon, and stars at different places, times, dates, and elevations.
Measure the elevation of the sun at different places, times, dates, and elevations.
Measure the distance between two locations which have 1 hour separating local solar noon.

What other observations and measurements have others taken?