A bridge was designed to go between Germany and Switzerland over a river ravine. Each country employed and dispatched their own surveying and construction firms for the work. the Swiss team used a vertical benchmark based on the Mediterranean sea level. The problem was the German group used a different sea level referenced to the North Sea, which is 27 centimeters different. When the German group applied the correction, it was inadvertently subtracted instead of added, so the error was compounded to a resulting 54 centimeter vertical difference. These are the results of the two bridges when they met.

Benchmarks matter. Vertical datums matter. Correct applications of those datums matters.

Better data. Better design. Better build.