Sight Polaris on your sextant. Drive 111 km south. Sight Polaris on your sextant. Repeat.
Who did this for the entire earth, or even once?
Celestial navigation has not only been used for hundreds of years, but it was accurate enough to not only get you where you wanted to go, but to map out exactly how you got there.
For hundreds of years ship wrecks have also been common and many innocent lives have gone missing to the sea. What is your source of navigational accuracy?
Your FE model even says celestial objects will move steadily across the sky with distance. If you deny this happens, then again your model has serious problems as sunsets are supposedly caused by distance. As the sun goes from directly overhead to a few thousand kilometers away it drops steadily toward the horizon until it vanishes. Why should the same not happen to Polaris?
The sun is not Polaris. It does not follow that they behave exactly the same. Polaris is at a higher altitude than the sun in the Flat Earth model, for one.
You can also use GPS. However it work--be it LORAN or GEO satellites, you can't argue that it doesn't actually work. GPS constantly confirms that 1° latitude is 111 kilometers.
GPS doesn't 'confirm' anything. Is it verifying the degrees of Polaris from your horizon when it tells you that you are at 25 degrees North?
A few commercial flights fly directly north-south, such as Atlanta-Lima. The latitudes of these places are known, and after decades of flying so is their distance. The combined information from all north-south flights can also show is that 1° is 111 kilometers.
Who calculated that?
1: This is a worse argument than creationists asking for transitional fossils and when being shown one asking for the one in the new gap, have you measured latitude inbetween measured points A and B. Navies from a host of nations, UK, France, Spain, Portugal, Holland, US etc have been plowing the seas for centuries, explorers and surveyors have made increasingly detailed maps and measurements.
2: For hundreds of years hundreds of thousands of ships have traversed the Earths oceans, the success rate is much higher than the fail rate. Also crashes are usually due to factors other than navigational errors such as storms or equipment failure.
3: According to you Polaris is only 100 miles higher than the sun.
4: GPS wouldn't work (and it does work) if the distance between lines of latitude wasn't accurate.
5: Now you're just being silly and arguing a point for the sake of it as opposed to having any reasonable reason to disagree. In fact that's all your arguments ever are!
6: Is your point of view then that there isn't a reliable Flat Earth model that can make predictions for stuff like sunrise and sunset and the suns position at different points through the day?