Geographical Survey Institute, Japan
Geographical Survey Institute (GSI) operates 5 VLBI stations (Shintotsukawa, Kashima, Tsukuba, Chichijima, Aira) and 959 GPS stations (GEONET: GPS Earth Observation Network) nationwide. To connect the two networks we employed local survey at each VLBI station. The methods we used are by GPS and by total-station. In GPS survey, coordinates of a GPS antenna attached to the VLBI antenna were measured from the nearest GEONET stations. VLBI antenna pointed every possible direction horizontally and vertically. The measured precision was 5mm for horizontal component and 2cm for vertical component. It contains IGS point and VLBI ITRF Reference Point. We are convinced of that this tie improves accuracy of ITRF in Asia Pacific region.