Laufenburg bridge · 2004
Laufenburg: 27 centimetres, subtracted instead of added, became 54
Germany measures height from the North Sea and Switzerland from the Mediterranean. The 27-centimetre offset between them was known, drawn correctly, and applied with the wrong sign.
The town of Laufenburg sits on both banks of the Rhine. Half of it is German, half Swiss. In 2002 the two halves began building a bridge toward each other.
When the spans met, one end was 54 centimetres below the other.(Verified)Nobody had mismeasured.
Height is measured from somewhere
Every height on a construction drawing is a distance from a reference surface, and the reference surface is a choice. Germany measures from the North Sea. Switzerland measures from the Mediterranean.(Verified)
Those two seas do not sit at the same level. The offset between the two national reference surfaces is 27 centimetres.
This is not obscure. It is the first thing a surveyor working a border river deals with, and the people on this project dealt with it. The project manager for the Swiss canton of Aargau, Beat von Arx, put it plainly afterwards: the difference of 27 centimetres was certainly known, and everything had been drawn up correctly on paper(Verified) .
The drawings were right. The correction was right. The number 27 was right.
The sign
On the Swiss side, the 27 centimetres had to be added. It was subtracted.(Verified)
A correction applied with the wrong sign does not cancel. It lands the same distance on the other side of the target, which puts the total error at twice the correction.
Source: Stuttgarter Zeitung, 20 January 2004
This is the arithmetic that makes the case worth telling. A forgotten correction would have left a 27-centimetre step. An inverted one leaves 54. The error is not the size of the thing you got wrong; it is twice the size of the thing you got right.
Why nobody caught it
A bridge built from both banks gives you nothing to check against until the end.
Each side worked outward over the water, level and straight, exactly as drawn. Both halves were internally consistent. There was no reference on the far bank to compare with, because the far bank was the thing being built toward.
So the crews found out the only way available. The mistake became apparent as the crossing neared the German bank.(Verified)
Construction had begun in 2002, with completion planned for the end of 2004.(Verified)Dates this article does not use
The second one is a small thing, and small things are where this goes wrong. A date nobody checks is repeated until it is furniture. Then it is quoted back as corroboration.
One source
This article rests on a single document: a contemporaneous newspaper report that quotes the named project manager, republished by the Dutch vertical datum authority. That is one organisation, and it is the strongest record available for this case.
A second organisation would make the dates firmer. Until there is one, the dates stay as stated above.
The next case is larger by three orders of magnitude and involves nobody making an arithmetic mistake at all.
Cut register
Figures that circulate and are not published here
- 1876 DISPUTED A search result asserts it. The primary source says construction started in 2002. The 1876 date belongs to an earlier bridge at the same town.
- 2003 UNVERIFIED Widely given, and absent from the retrieved source, which is dated January 2004 and gives no discovery date. This article dates the case to the report.
- −54 cm UNVERIFIED The retrieved source describes the discovery, not the remedy. How the two halves were brought together is not stated here.
Sources
1 entry · 1 organisation
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S01
Stuttgarter Zeitung PRIMARY
The bridge at Laufenburg (translation of Stuttgarter Zeitung, 20 January 2004)
Contemporaneous reporting that quotes the Swiss project manager by name. Retrieved as an English translation published by Normaal Amsterdams Peil, the Dutch vertical datum authority.
Accessed 11 September 2026