We use the VGOS session VR2101 to assess\ua0parameters describing the signal delay in the neutral\ua0atmosphere. VGOS results are compared to corresponding\ua0results derived from co-located GNSS stations\ua0for all sites, and additionally to results from a\ua0ground-based microwave radiometer for the Onsala\ua0Space Observatory. For the first time all three independent\ua0techniques can be compared with the same\ua0high temporal resolution of 5 min. Zenith total delays\ua0from VGOS and GNSS reveal correlation coefficients\ua0larger than 0.9 for all but one of the participating sites.\ua0Corresponding offsets are between 1–8 mm and root\ua0mean square differences are between 4–14 mm. Horizontal\ua0gradients from VGOS and GNSS have correlation\ua0coefficients between 0.2–0.5 for the east components\ua0and 0.4–0.7 for the north components. Corresponding\ua0offsets are sub-millimeter, and root mean\ua0square differences are on the order of 0.5–2.2 mm.\ua0The comparisons for the Onsala site of VGOS and\ua0GNSS w.r.t. microwave radiometer show correlation\ua0coefficients larger than 0.96 for the zenith total delays\ua0with offsets on the order of 7–11 mm and root mean\ua0square differences of 9–12 mm. Horizontal gradients\ua0show correlation coefficients of about 0.2 for the east\ua0components and about 0.5 for the north components.\ua0The corresponding offsets are between 0.6–1.8 mm and\ua0the root mean square differences are 0.9–1.3 mm
