- Lt. Col. Thomas Lincoln Casey, 1885
There are a number of known reasons why the value obtained in 2014 for the architectural height of the Washington Monument disagrees with the original 555 feet, 5 1/8 inches and the 1999 value of 555 feet, 3 5/8 inches:
- The 1885 Archtectural Zero Height Point (the place where Lt Col Casey considered height to be "zero") remains unknown.
- However, assuming the hypothesis made in 1999 is correct, the CTBUH standard places the AZHP at 0.220 meters (8 5/8 inches) above the 1885 location.
- The peak itself lost 3/8 of an inch since its original placement due to rounding (from erosion and/or lightning strikes).
- Surveying technologies have changed significantly since 1885, and measurements easily performed in 2014 were not possible in 1885.
