The convergence of meridians toward the South Pole causes unique problems for geometrical comparison of
structural geological and geophysical datasets from Antarctica. The true North reference direction ordinarily is used for
measuring and reporting vector data (strike, trend) in Antarctica, as elsewhere. However, over a latitude distance of just
100 km at 85° South, the angular difference in the true North direction exceeds 10°. Consequently, when performing a
regional tectonic analysis of vector data (strike, trend) for structures such as faults, dike arrays, or geophysical
lineaments oriented with respect to North at different sites, it is necessary to rotate the data to a common reference
direction. A modular arithmetic function, performed as a spreadsheet calculation, offers the means to unify data sets
from sites having different longitude position, by rotation to a common reference direction. The function is
SC ≡ SM + ∆L (mod 360), where SC = converted strike; SM = measured strike; ∆L = angle in degrees longitude between
reference longitude and study site; and 360, the divisor, is the number of degrees in Earth’s circumference. The method
is used to evaluate 1) paleomagnetic rotation of the Ellsworth-Whitmore Mountains with respect to the Transantarctic
Mountains, and 2) orogenic curvature of the Ross Orogen
