The engineering feat behind the Great Pyramid of Giza was so impressive it is not surprising the monument made it as one of the Wonders of the Ancient World.

A new survey of the pyramid, however, revealed that the structure, the oldest and biggest of the three pyramids lying in the Giza pyramid complex, was not perfectly built.

Researchers have found that the structure's base is slightly lopsided. Egyptologist Mark Lehner and engineer Glen Dash discovered that the pyramid's west side is longer than the east side.

The discrepancy is just a few inches but the difference was enough for the researchers to detect.

The pyramid was originally clad in hard, white casing, but much of the casing stones are now gone. Without the casing, researchers have had difficulty getting the precise measurements of the pyramid when it first stood.

In an attempt to know the original lengths of the pyramid's sides, the researchers looked for marks that indicate the original casing baseline of the pyramid. These were points where the casing stones once touched the platform.

The researchers eventually found 84 points along the edge of the pyramid where they found evidence of the building's original baseline. These were then marked on the Giza Plateau Mapping Project (GPMP) control grid, which is used to map all of the features on the Giza Plateau.

A statistical method called linear regression analysis was then used to determine the lengths of the sides, revealing that the pyramid's east side originally measured between 755.561 and 755.817 feet. The west side, on the other hand, was found to be originally between 755.833 and 756.024 feet.

Unfortunately, because of uncertainties on how the ancient Egyptians built the monument, researchers are not exactly sure where the error came from. It is, however, possible that it was the result of mistakes committed by builders during construction.

Because the west side was 5.55 inches longer than the east side, it means that the pyramid was not a perfect square. Nonetheless, the researchers said that the pyramid, having been constructed more than four millennia ago, shows its ancient builders' impressive level of precision.

"Our survey has produced new estimates for the size and orientation of the Great Pyramid," Dash reported.

"We hope to eventually figure out how the Egyptians laid out the pyramid with such precision, and in doing so hope to learn much about the tools and technology they had at their disposal."

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