Surveyors, engineers, and architects never factor in the supposed curvature of the earth into their projects.
Never? Are you sure about that? How do you support that claim?
What about these examples?
Because of the height of the towers (693 ft or 211 m) and their distance from each other (4,260 ft or 1,298 m), the curvature of the Earth's surface had to be taken into account when designing the bridge. The towers are not parallel to each other, but are 1 5⁄8 in (41.275 mm) farther apart at their tops than at their bases.
A description of J-PARC, including the effect of the curvature of the earth on the design:
http://www.slac.stanford.edu/econf/C06092511/presents/TU004_PPT.PDFObservation height of 120,000 ft ... we can observe it's perfectly flat ...
I don't believe that you have ever personally observed that. You have only relied on photographic evidence, which according to FE cannot be trusted because it can be faked.
Perspective over the plane ...
Interesting! If the Sun is 3000 miles above the earth then how does it shine on the
bottom of the clouds in your picture?