I've read somewhere from the internet that a nautical mile was originally an unfixed unit of a minute of a degree of latitude, measured relating to the North Star using navigational sextant. Wikipedia explains that latitudes are measured in relation to the center of the globe which makes them all equal, but i cannot imagine how a navigator could practically find the center of the earth for determining the latitude.
So do our latitudes as given by GPS coincide with the readings of a sextant with the North Star? Googl brings up the definite yes answer, but it couldn't be true if the world isn't a globe. Or maybe latitudes coincide, while actual distances between them differ, ie how the cover-up would be achieved, what data is forged? The factor of 1/800 doesn't seem much, has anyone calculated how far the North Star has to be to produce such difference, assuming the earth to be flat?
Did Cassini measured the North Star from the sea level, or on what altitude? I guess it can change the outcome, if stars are actually nearer to earth.
When you have time, i would welcome your info.