Flat earthers have not ignored geodesy. https://www.bitchute.com/video/g1QZEJ3fXXe3/ But ball earthers have ignored the other measurements provided by science. "In their quest for victory [ball earthers] have jettisoned all reason."
Now what this character in your video is doing is trying to convince himself and flat-Earthers that this science of geodesy is bull. He asserts that geologists for over 300 years didn't know what they were doing was illusionary. At 38 minutes he tries to make a laugh at the way this science works. You see some of us know the Earth has seas, land and mountains. In other words the surface is not even. But we know the seas are even and if we use the seas as the standard surface measurement the science can work out more accurately the distance between areas and work out its bend. This of course it too complicated to your man to understand.
This science was used by Domenico Cassini to falsify Newton's evolved bulging Earth. Cassini remember was the first astronomer to work out the distance of the sun from the Earth. Cassini’s talent as a surveyor was also well known. In 1657 he was asked by none other than Pope Alexander VII to resolve a dispute regarding the flow of the River Reno between Bologna and Ferrara that was causing flooding. For the next seven years Cassini was occupied with similar work around the Papal States. Cassini's Geodesy is but an extension of his surveying.
It is possible to determine the shape of the Earth by measuring the length of an arc corresponding to a geodetic latitude differences at two places along the meridian (the ellipse passing through the Poles) at different latitudes, which means at different distances from the Equator.’ With the aid of his son Jacques Cassini (Cassini II) and others, he measured the arc of meridian from Paris north to Dunkirk and south to the boundary of Spain, and, in addition, he conducted various associated geodesic and astronomical operations that were reported to the Academy.
The results, published by Cassini II in 1720, showed the length of a meridian degree north of Paris was 111,017 meters or 265 meters shorter than one south of Paris (111,282 meters). This suggested that if this trend occurred in the southern hemisphere, the Earth has to be a prolate spheroid, not flattened at the poles as Newton proposed, but slightly pointed, with the equatorial axis shorter than the polar axis, that is, kind of egg-shaped rather than orange shaped.
Flatearthism has no doubt many good arguments to explain how it could work. But it also depends on there being a long conspiracy to hide this from the world, with many thousands of people all involved in making sure this 'secret' never came out. It denies all space photos or images of a curve by satellites we can all see moving above the Earth, allowing us the E-mail and phone each other from one part of the Earth to another. Best of all however, is that the biggest problem for flatearthers is to keep the edge of their Earth out of sight from anybody when all they need to do to convince all that the Earth is indeed flat by flying a plane, a spaceship, a balloon or a drone over the edge of their flat Earth taking videos or photos of it. Now that should convince everybody. So, who don't they do that? I tell you I for one would have to accept that as the only real proof for a flat Earth.