Navigation has nothing to do with the shape of the world.
Communication has nothing to do with the shape of the world.
Civil engineering has nothing to do with the shape of the world.
So you think navigating around the world has nothing to do with the shape of the world?
Do you know how insane that claim is?
A key part of navigation is maps.
Maps are intrinsically linked to the shape of the world.
Even things like communication do depend on the shape of the world, as the shape of the world places limits of how far you can communicate, and has very significant implications for satellite communication.
Navigation has always been performed the exact same way.
Really?
The ancient people of Earth had GPS and maps built into their phones?
That is the first I have heard of that.
How often do you use the stars to navigate, vs GPS?
Also, even navigation based upon the stars, over all of Earth, requires Earth to be round.
Using the celestial poles (there are 2 of them) to determine your latitude, requires Earth is round, or else the math would be vastly different.
The celestial pole is at an angle of elevation equal to your latitude, BECAUSE Earth is round.
It is doubtful any of it takes place via satellites.
Land based communication is much more reliable and is still the primary method.
And you not liking reality won't change it.
If it all takes place via land based methods, why do satellite dishes for TV point to satellites in geostationary orbit rather than a land based tower? If it is all land based, why don't they just have normal aerials like normal land based TV transmission?
Why do sat phones and GPS manage to get a signal where land based phones don't?
Why does it sometimes work the other way around as well, where you can be inside a building and a normal phone works fine while satellite based communication doesn't because of all the building above you?
None of it requires spherical trigonometry!
It does if you want to have the road go to its destination.
This is intrinsically tied to mapping as well.
If you try to map Earth as flat, it simply doesn't work.