How long is a German foot? It depends where you are

Of course. "Germany" was splintered into many, many small fiefdoms and bishoprics, all with their own coins, weights and lengths.

But it's not really different from the nautical mile, International mile, English mile, Welsh mile, Scots mile, Irish mile, or any other of the handful of "miles" that existed.

Should be better "was" a German foot. We have the metrical system since the 19th century.