See Chapter 3 and Figure 63.

In the Parthenon, the long north flank of the stylobate has survived in a suitably well-preserved condition to allow for a detailed study of the measurements of its curvature. G.P. Stevens established seventeen coordinates documenting the incremental rise of the stylobate to a maximum rise of .103 m in the center of this dimension of 69.512 m long. One minor complication in analyzing the curvature is that the two ends of the stylobate are not level, with the temple's northwest corner instead raised ca. 3 cm with respect to that of the southwest. As discussed in Chapter 1, there is some question as to whether this rise and that of the southwest corner (5 cm) represent inaccuracies of construction or deliberate “refinements of refinements” intended to correct an optically inferred convergence in the curved lines that would otherwise take place from the perspective of the Sacred Way (Figure 21). As a result, the theoretical baseline below the curvature is inclined with its slightly diagonal rise ca. 3 cm over the 69 m + distance from east to west. Seybold resolves this inconsistency by analyzing the ordinates in relation to the x-coordinates along a theoretically level baseline corresponding to the easternmost point at 0,0. This method in no way compromises the results because, in the end, an identification of the nature of the curvature (i.e., its optimal conic section) is not affected by this baseline's inclination of less than .03°.