There's a race where they circumnavigate Antarctica. https://www.sail-world.com/Australia/Antarctica-Cup-Yacht-Race/-36654?source=google
Do they turn towards Antarctica, track straight or away from an ice wall? Flat earth would be away from it.
Takes about 100 days
https://www.sail-world.com/Australia/Fedor-Konyukhov-sets-Antarctica-record/-44187?source=google
At 66,5 N or S. the circumference is 8,620 nm or 16.000 , on a Flat Earth at 66.5˚S it would be 19,800 nm. or 37,000 km. So the race proves Earth is a spheroid.
37,000km in 100 days would be 370km/day, 15km/h average. Roughly double average cruising speed.
Bislins has a ton of data you can run in his visualizations from boat races like this: Link
You can download landsat mosaics here https://lima.usgs.gov/fullcontinent.php
https://antarctica.anthropogeos.com/en/introduction
IN THE 2019-2020 SEASON, THE ANTHROPOGEOS TEAM WENT ON AN EXPEDITION ACROSS THE CONTINENT, JOINING THE COLONIALIST MOVEMENT. THIS TRIP BECAME THE BASIS FOR THE PROJECT ANTARCTICA. THE LAST COLONIZATION. WE DROVE 4500 KM THROUGH THE WHITE DESERT AND WE WANT TO SHARE OUR EXPERIENCE, AS WELL AS EXPLORING THE INS AND OUTS OF TOURISM AND LIFE IN ANTARCTICA.
They used Arctic trucks, one of the three tourism agencies allowed to operate in Antarctica.
https://arctictrucks.com/polar/
https://www.arctictrucks-experience.com/antarctica/
http://antarcticachallenge.com/antarctica-crossing/