Abstract The ionospheric path delay impacts single-band, very long baseline interferometry (VLBI) group delays, which limits their applicability for absolute astrometry. I consider two important cases: when observations are made simultaneously in bands, but delays only one band available a subset of observations; and one-band design. developed optimal procedures data analysis both cases using G...

We present a robust and fast algorithm for performing astrometry and source cross-identification on two dimensional point lists, such as between a catalogue and an astronomical image, or between two images. The method is based on minimal assumptions: the lists can be rotated, magnified and inverted with respect to each other in an arbitrary way. The algorithm is tailored to work efficiently on ...