An Interpretation of the Ambiguity between Annual Terms Obtained by Time and Latitude Observations

Abstract

Guinot and Feissel (1968), Okazaki and Nasaka (1970) reported the marked discrepancy between annual terms of the polar motion obtained by time and latitude observations. The disturbing effects of local non-polar terms in latitude variation on pole coordinates are discussed in the first half of this paper.

From an analogy between time and latitude observations, we can conclude that Δx and Δy in the pole coordinates obtained from time observations are proportional to a part of the common fictitious term ΔT in the rotation of the Earth. Using ΔT obtained from Okazaki's data for the same interval as Guinot's and Feissel's data, a test example is given as follows: If we apply the above corrections to the pole coordinates obtained from time observations, we can derive the coordinates x and y which are comparable to those of the ILS. Δα_α, ΔS and local non-polar terms (z₅ – z₄) in the ILS latitude determination may be considered as the sources of ΔT.