Comparison of Doppler and Optical Pole Position over Twelve Years.
NAVAL SURFACE WEAPONS CENTER DAHLGREN LAB VA
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Positions of the earths spin axis with respect to the crust are computed by three independent systems using data from the 5 International Latitude Stations ILS, using data from 40 or so astronomical observatory stations submitting data to the Bureau International de LHeure BIH, and using data from 20 or so Doppler stations in the Defense Mapping Agency DMA network. DMA data for the 1964-1970 period have significant errors due to approximations in computational methods used in this period. ILS data for the period 1970-1975 have significant periodic and a secular differences from BIH or DMA data as compared to the consistency between BIH and DMA data. Author