Jet core relative positions of FIRST J222112-012806 measured with respect to the jet cores of three reference sources (i.e., ICRF J221852.0-033536, ICRF J221947.2-005132, and ICRF J222646.5+005211) at five observing wavelengths. Systematic uncertainties calculated with Eq. (1) have been included in the positional uncertainties. Models of the combined core shifts are derived assuming ${\beta }_{i^{\prime }}\equiv 1$ with Bayesian inference (see Appendix E), and displayed with straight lines.