On the precision estimates of Earth gravitation field models

Formal estimation of the random component in global maps of total electron content

“…Helmert transform (HT) and singular spectrum analysis (SSA) in one-dimension variant were used by author and his colleagues in their works [1,2,3,4,5].…”

“…All les containing TEC maps in IONEX format have been taken from NASA server 1 Very short information about the data sources is given in Table 1. Dierent les contain dierent amount of maps calculated for dierent time moments inside the day.…”

On the extension of Helmert transform

“…He introduced shift plus rotation transform. It is widely used until now, see for example [2,3,10], and not only for TRF/CRF comparison [4].…”